Town MPG in a CTD
 

After joining Team Cummins a while back, and carefully reading what Diesel_Dave was doing on his truck I made some changes.

Several years ago had settled into a routine that was easy (the point of it) where all miles were covered between 1,700-1,900-rpm, town or country. The gearing of my truck (transmission and rear axle) meant that speeds of from 33-63 mph were easily covered by driving in 4th, and rarely in Direct in town, and OD for country (1,725-rpm at 58-mph). This might mean 33-mph in a 40-mph zone. A 7,500-lb truck is hard to stop, and keeping a bit of engine rpm to accentuate engine braking was found optimal by me. On a 45-mph road with little chance of cross-traffic I would upshift to Direct and run a bit faster.

This brought my town mpg from 18 to 19+ mpg, annual average over several years, and country mpg to 24 in all solo conditions (traffic, weather, payload, etc).

I gave myself room to be sloppy. And left room for when the weather was hottest (extended idling to maintain cab cool). The point of simplicity is that it is easy to follow with a minimal set of guidelines, and might be followed even if sick or injured or just plain tired.

I have always driven for mpg since acquiring a drivers license nearly 40-years ago, so a pretty fair amount of this -- EM suggestions -- was not new. More important to me -- much more important -- than mpg is vehicle longevity, followed by reliability. Mpg is third at best. Questionable practices -- EOffC -- were never considered.

So the second change I'd instituted just prior to joining here a couple of years ago was to reduce the total number of trips, even if each trip was longer by several measures available. The vehicle that doesn't move doesn't burn fuel. And when it was turned on, a route to all places was in hand with a considerably long warm-up drive favoring the local freeways to the farthest point first and then working back to the start point (home).

So far, so good. But I noted Dave's numbers, and -- even though I am not a commuter with set departure times and routes -- I felt I could improve my majority (at this time) town mpg. When he noted that Cummins had stated that the (later) 6.7L engine had it's best FE in the 1,300-1,500 rpm range and that he rarely saw above 1,600-rpm, and that it is possible to have higher town than country mpg the lightbulb went on.

So I moved things downward. All miles (as possible) at 1,300-1,500 rpm and shifts at about 1,500-rpm (and a hair upwards) to bring the engine back in at around 1,100-rpm. I was uncomfortable previously in bringing it back in at lower than 1,300-rpm (torque peak is 1,600-rpm) as that was part of my training in big trucks (respecting peak torque). City freeways are now covered at about 53-4 mph at 1,600-rpm.

I've recently averaged above 23-mpg "town" over more than a thousand miles with, again, these simple changes.

Thank you, Dave. First for me among the many around here as our vehicles are so similar; setting a larger context for me to read more carefully what others are doing.

For you other CTD drivers I've been able to up my average mph to 28+ in this period. Anything above 25-mph is optimal to the best of my experience.

Now I'm stoked to change my rear end gearing to 3.42 from the present 3.73 as that will bring me into the 1300-1500 sweet spot for nearly all town driving, and quite close on country driving. I'll give up a little perfomance, but as I am full-timing (living/working from a 32' travel trailer) this matched pair rarely exceeds 16,000-lbs -- low for this trucks capabilities; not considered "heavy" -- the change makes sense. A marginal change that will add up over the expected years and miles this vehicle will be in use.

I've also yet to explore slightly advanced engine timing and it may be that both changes will occur this calendar year (along with some small changes on intake and exhaust that mirror later factory practice).

I may also do some changes to reduce NVH (and hopefully extend vehicle life) that could have an effect on mpg, namely, changing to a lighter one-piece driveshaft and to a fluid-filled harmonic dampener (as the factory has, again, done in models later than mine). The effect may simply be indirect: a more alert driver on long trips.

A winter front, engine heater cord and a partial grille block have long been on the list. 2012 ought to be fun (more of the easy gains).

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Bravo! I think respecting peak torque when your engine has a boatload of it to spare is not necessary :D
If I light-foot my auto it stays around your goal RPM with the 3.55s. 55~60 MPH is around 1700~1800.

Way to go, man! Keep up to good work.

I've been looking at doing a rear axle swap, too. I'm thinking it's easier to swap axles rather than gears (less to mess up). When I get around to it, I was going to just put a post up on Cummins Forum offering to swap somebody in my area a 3.73 axle for a 3:42. That way there's no cost involved, just a little elbow grease. The key would be finding somebody who has comparable miles and hasn't abused it.

Thanks. I've been running country miles at 1,725-rpm or 58-mph since earilest 2009. I'll find a calculator and post what the numbers "should" be with a gear swap from 3.73 to 3.42 on these stock spec tires.

Loaded or empty, rain or shine, day or night, I put 16k on the truck commuting back and forth to another Texas city twice monthly that year and into 2010. Had to cross Houston each leg of the trip. Never saw lower than 24-mpg, with some highs around 27 (shown in fuel log where I went for "racetrack mpg": filled after warm-up and re-filled before shutdown to see what potential highest could be). Also, I kept the tires at the factory spec of 50/50 in psi FF/RR.

As to torque, it was pointed out that, again, the 6.7L (with a different manual transmission: the Mercedes-sourced G56) has an engagement torque of 400-ft/lbs. I'll assume my eariler New Venture 5600 (behind a motor with lower HP/TQ numbers) is similar. Indeed, I have to really come back in at a low rpm (sub-1,000) before I hear the auto-throttle take over and get a touch of rattle.

EDIT: Next step is in weighing this truck on a CAT Scale to get the current "solo" weight per axle and combined (driver, full fuel plus current bed load anticipated to change little) so as to dial in tire pressures ideally. I've experimented with 52/73 FF/RR recently and today dialed it back to 55/55 [hot] as the higher pressure in the rear screws the handling too much.

I have to move the trailer in another one or two weeks, and I'll get numbers for it as well at that time. As I have to install a new hitch receiver I'll be able to crank in the weight adjustment better than before.

Afterwards I'll have both solo and towing tire pressure numbers to work from.

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1725 X 3.42/3.73=1581.6

regards
Mech

Thanks, again. Your insights are a real help.

There is a fairly long thread on the 3rd Gen trucks on CF in re this gear swap. Several good reports. For the 6.7L guys, see posts by CourierDog a hotshot owner/op out of central Alberta seeing 20-mpg after this swap on his early (badly geared) G56.

As my truck just turned over 180,000-miles at 4,600+ hours I am working from the premise, that, as the average mph on the truck is above 35-mph during my ownership period, and was at 47-mph with the previous owner, I am hoping that I am now at the halfway point in time and miles (per 15-year standard life, and slipping past the B50 or MTBO of 350k due to miles/hours relation). Thus my plans are of running this truck another eight [8] years and another 180k miles. Any drivetrain related upgrades would then have the time/miles to pay out in a reasonable fashion.

I am, then, considering sending a new AAM 3.42 gearset and master overhaul kit to MICROBLUE RACING for their proprietary work (as well as axle end bearings) due to some highly favorable experience being shown on the Let's Truck forum (threads by Dice1). 4/10's of a mpg consistently on big trucks with wheel bearing changes; tractor and/or trailer. If I also source the TT wheel bearings through them I am hoping for a bit of elbow room, overall, when towing conditions are otherwise difficult. I would like to see a 1-mpg gain for the rig where both vehicles are as well set up as possible (drivetrain [and related] efficiency).

As of today were I to overhaul the NV-5600 I might also send it out for the same work. All of this is expensive with a payback that is more about friction reduction (temp control, thus fluid life) with a possibility of mpg help. Sort of a "create favorable mechanical conditions" scenario.

23-mpg around town wasn't new. But for over 1,100-miles it sure was. I'm pleased to accomplish that, and can now see where spending money will be able to make money as the payout will be of reasonable length. And to have some fun with gold-plating a few items.

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Thanks, Old Mech. It does look pretty much like a 200-rpm drop.

As I tend to forget the details of truck spec and gear numbers I'm going to lay it out in this post I can reference in future; to show a range of what travel speeds can be made with the 3.42 across the ideal 1,300 - 1,500 rpm range per gear choice.

The calculators by Bowling & Grippo are an old favorite of mine from when I was researching how to get max FE from a big block Chrysler set up for TT towing a dozen and more years ago.

NEW VENTURE 5600: This six-speed is used in light duty Dodge pickup trucks from 1998-2005. All forward speeds are fully synchronized. This unit has an aluminum bell housing, cast-iron case & extension housing with a top mounted shifter. Available in both 2WD and 4WD versions, this unit weighs 360 lbs. The transmission is rated medium duty capable with a GCW of 26,000-lbs.

Transmission Ratios:

FIRST 5.63
SECOND 3.38
THIRD 2.04
FOURTH 1.39
DIRECT 1.00

OVERDRIVE 0.73

Stock tire size is 265/70R-17 31.4" tall at 657-rpms per mile
(MICHELIN LTX A/S Load Index 121 (E-Range)

With these book numbers entered it looks as though I'd be able to run:

* School zone at 20-mph in Fourth at 1,081 (or in Third at 1,494-rpm)

* Town at 30-mph in Fourth at 1,527-rpm

* Town at 35-mph in Direct at 1,281-rpm

* Town at 40-mph in Direct at 1,464-rpm

* Town at 53-mph (freeway) in OD at 1,416-rpm

* Country at 55-mph in OD at 1,470-rpm

* Target: 57/8-mph @ 1,523/1,550 rpm

(Versus current rpms of 1,725/50-rpm at this speed)

* Country at 60-mph in OD at 1,604-rpm

In other words, all 20-40 mph town driving, and all 55+ mph country driving is within or just barely atop the 1,300-1,500 desired rpm range. Can't ask for more than that! To my way of thinking, no need for a high-maintenance, questionably reliable Gear Vendors second overdrive unit (at $4000) or in changing tire size.

Winding out each gear a bit further than at present (time/distance, not rpm) ought to also make for some smoother transitions if I am correct.

As the range for towing is generally 1,400 - 2,200-rpm I ought (with this type of lightweight aero TT) to be able to maintain headway on the flats barring bad crosswinds at these same rpms, and still be able to "pull" the mountainous terrain at only a slightly slower speed than before (and nothing was slower than a few of the big trucks I've driven).

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I think your 5.9L probably has pretty similar clutch engagement torque as the 6.7L. I'd say over 350 ft-lbs easily.

Regarding the "auto-throttle" you're correct. The low-speed governor will not engage until you dip below the idle speed. For me that's 800 rpm. I think it's the same for you. Basically the low-speed governor is there to prevent stalling--if you load up the engine so much that the speed dips under idle speed it adds more fueling to try to get the speed back up to at least idle speed. Of course, it can only do so much. If you try to start off from a dead stop in 4th gear and just dump the clutch it'll stall anyway, because it can't react that fast.

By the way, do you know how to find out the "official" towing capacity of the truck (GCWR)? I assume that depends on the tranny and axle that you have, so do you have to have Dodge look it up for you based on the VIN number? All I can find on my door sticker is the GVWR.

The Dodge Towing Guide is the way to finding specific of the question.

(The Dodge Bodybuilder Guide is the second source of this type of information).

On mine: (the closest choice set)

2004 Dodge Ram pickup 2500 SLT, QUAD CAB, 2WD, 8.0 FT Bed, 6-Speed HD Manual Transmission, 5.9L Cummins Turbo Diesel Engine - 610 lb-ft:

With 3.73 Axle Ratio Axle Ratio You Can Tow 13,100 lbs
Gross Vehicle Weight Rating (GVWR) = 9000 lbs
Payload = 2274 lbs
Curb Weight = 6726 lbs
Curb Weight Front/Rear = 4071 lbs/4071 lbs
GAWR Front/Rear = 4750 lbs/6000 lbs
Gross Combination Weight Rating (GCWR) = 20000 lbs

One takes the vehicle to a CAT Scale to find:

With driver, full fuel and items in truck that are always aboard, the "new" FF and RR axle weights plus combined numbers. This gives the proper "empty weight" to then calculate remaining payload capacity, etc. The first step in setting up a tow vehicle is to run the numbers (as is the last). While the truck is capable of higher towing numbers than those listed, one must respect tire loadings (and gamble a bit on RR axle rating; luckily commercial operators blazed this trail for us).

Proper tire pressure is about knowing the loading per wheel; generally, it is averaged across the axle. Note that combined GAWR's are higher than GVWR.

Hitch rigging is dependent on knowing proper "empty weight" as well as "hitched, but WDH inactivated" and "hitched, with WDH activated" numbers per axle [set] as it includes the trailer; the differences between axle values from solo to towing.

My truck weighs 7,360-lbs until recently, with topper, bed liner, driver, full fuel and a couple of tubs of stuff in the rear. It is now higher with full-timing load.

I'll acquire a new "empty weight", and then drag this trailer across the scales to find the other two number sets (plus trailer axle and tongue weights separately).

Start with numbers, end with numbers.

Much of what is constituted thus when we speak of longevity (component life, then vehicle life) is a matter of getting the numbers right. Reliability is on the same curve, so to speak.

FE is more easily achieved when weight is properly distributed (bed load, and any trailer loads) so that braking and handling is least affected. This includes tire pressure numbers: derived from actual loading.

The goal, as I see it, is to remain lane-centered going down the road with zero or very little driver input to maintain headway. Any driver input necessary to correct to this state of speed and position -- be it throttle, brakes, or steering -- is detrimental to longest life, highest reliability and thus to FE.

EDIT: The main point to working the numbers while towing is for the trailer, in a manner of speaking, to have no effect on the truck . . missed by many is that we also want the truck to have no effect on the trailer. It really is a two-way street, and the truck (when a truck is the tow vehicle) can be the weak link in the chain of road performance (which is also safety).

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Highway Round Trip
 

Well, here's a bookend to this thread:

Had to make a run to Houston yesterday to buy an RV air-conditioner. Cost of freight on that item was high, and with no local deals worthwhile, I took advantage of being in a big metro area to source a few other things for truck & trailer along with a truck service not available to me elsewhere.

In trip-planning the roundtrip point-to-point was 407-miles. Additional miles was figured at 80 (dependent on locally sourced information this might be higher, potentially lower. In fact it was much higher). True cost was around $230 (cpm calc), of which $110 was out-of-pocket when food/misc is included. Freight "savings" was about $180, plus a labor expense of $40, so $$ is a wash, thus, "success" [break even] in a full day of working the truck as the aforementioned exclusive service was also done.

Filled up first time the night before and hit the road at 0430 to make the 0900 service appointment. Fog for over 100-miles made it a stressful dark-o-thirty drive with that 99% humidity and temps mainly in low 60's. Had to move at 65-mph to be on time for about half the distance.

Returned last night by 21:30. Engine run time was 11.25-hours for an average of 47-mph. Felt like I was never out of the truck over that 17-hours, but 5.75-hours says otherwise (truck drivers are allowed 11-hrs driving in a 14-hr workday). Minor crosswinds outbound & inbound with temps from low 60's to mid-70's for the most part. Truck was heavy with a lowered rake on the way back (full-timer "trunk junk" and had to load the 105# A/C unit and new 90# Class V hitch receiver; respectively, at the very back of the bed, and literally just beyond/below the crossmember = pendulum effect) and A/C was on most of the day.

Fuel burn was 26.8-mpg where 360-miles was country, and 170-miles was Houston metro ("town" miles). Went through [22] engine starts with [17] departures.

Filled second time at farthest point from home, and then again the third time a few miles prior to final shutdown. Nearly the same distance and nearly the same rate of consumption. Made a point of using SHELL diesel as some hotshotters claim better running & mpg versus the more usual VALERO diesel. Might be something to that. Used the last of a gallon of SCHAEFFER's #131, so the combo worked well. OFL and new fuel filter the past two weeks. Tire pressure at 55-psi all around.

This is the first trip of any distance out-of-town on this truck in 1.5-years.

Keeping shift points low is really working well. I was figuring fuel cost at 16-cpm but came in at .145 instead.

I have been working from the premise of 21/town and 24/country when driving for economy (hottest weather excepted) over the past couple of years. Now have seen that 23/town and 26/country while solo is possible (all other conditions basically favorable). The last 2k miles have averaged 23.8-mpg . . nice to see that extra 9%.

I now feel it safe to estimate country miles at 4-gls/100-miles solo for level terrain & mild climate. This is versus quite a few -- maybe most -- diesel pickups at 18-mpg/country and is worth just over $2000 every 10k/country at today's prices. More importantly it's a reduction of 550-gls to do the same work over the same miles.

(I'm a good ways away from new towing mpg figures, but if I extrapolate based on the type of solo improvements made in the past five years, I could see mpg going from 15+ to 17+. That's just barely beyond what others with my spec of rig are seeing -- 16-mpg high cited often -- so the potential is there as this would not be the high number for CTD/aero aluminum TT owners; or, 6-gls/100-miles [22-cpm at $3.79/gl].)


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Way to go, man. Keep on truckin'!

Very nice. Good thread.

nice thread/read Ive been considering a rear end swap myself to improve mpg #s from 410s to 3.73s . I was worried about take off ,you guys dont seem to think its a problem with the higher gearing . But my 99CTD has an auto, do you think this gearing will kill my trans (may need an upgrade soon anyway) plan on pulling a 24ft viewfinder v-nose, so saving fuel is where its at

3.73s won't kill your tranny. If you are going to go to the trouble of changing your gears, you might want to go to 3.54/3.55 (that still won't kill your tranny). Going from 4.10s to 3.73 isn't much of a change.

I believe (but am not certain) that the CTD's are sold with identical transmissions regardless of the axle (4.10, 3.73, or 3.42). So I don't see how swaping one for the other would cause any tranny issues.

thanks. Ill talk to my buddy he works a one of our local wrecking yards so ill have him look for a low mile unit and ill change the whole rear

Update
 

I'm just about a year into my new life, post-divorce, where the truck has become the "garage" for tools/supplies/equipment. About 4-500/lbs of this will be removed once a new travel trailer is purchased, but some stuff in the current TT will be moved to the truck (truck bed specific toolboxes). Both vehicles will be undergoing changes, maintained, upgraded, etc., and the 130-c/f truck bed is where all this sort of thing is stored. My time to work on projects is limited, thus a place where the dirty stuff can go is a priority.

A recent set of scale weights showed:

Steer Axle: 4,100-lbs (4,750-lbs GAWR)
Drive Axle: 3,860-lbs (6,000-lbs GAWR)
Total: 7,960-lbs (9,000-lbs GVWR)

Individual wheel positions were also weighed, and the truck is within 40-lbs at all four corners.

The second set of OEM-spec MICHELIN LTX A/S tires -- with 11/32's of treadwear remaining at 68k miles -- failed on a highway trip at just over [5] years and were replaced under warranty with all-season MICHELIN LTX M/S2 tires. Same load spec range, and -- while also looked upon by MICHELIN as being "LRR" -- have shown a decrease in mpg (highway) of around 1-1.5/mpg. Still in first several thousand mile break-in period, though.

I expected to replace the A/S tires (closed shoulder, highway rib) with the M/S2 (or BRIDGESTONE Duravis m500) by the seventh year with all season type as the OEM tires were not so hot for wet or loose surface traction. An expected move north in 2014 means snow, and -- short of dedicated snow tires -- the mpg hit was already an acceptable trade-off. Another 2WD CTD owner in metro Denver reported good results with this tire. But I wasn't expecting to take a (retail) "hit" of $1,300 on tires this year. C'est la vie . . . .

With the new tires I'm using the DODGE numbers of 50-psi FF (all conditions) and splitting the difference of from 50 to 70-psi rear at 60-psi at present. After purchasing a new spare tire, I'll rotate more often (expecting shoulder wear on these tires the closed shoulder A/S didn't have) and look to find the "lowest" tire pressure I can run when solo (per CapriRacer the test of: after 1.5-hrs steady-state driving a pressure rise from cold to hot of no more than 10%) where DODGE numbers (projected at 15% load reserve above RMA) are in use.

Highway fuel economy has (at a lighter 7,350-lbs) not been below 24-mpg on level, near sea-level, Interstate higways, with highs of 27 (on a dead-stock truck) when at 58-mph (reference numbers).

Truck handling characteristics being what they are -- and tire wear being low by following DODGE guidelines -- the "supple" quality of proper load range tires via recommended pressure is a distinct aid to handling. Too high pressure in the rear, for example, exacerbates tail-out tendencies (and rollover propensity). That the first set of tires went 120k, and that the second set was on track to exceed 150k (by treadwear) bore out this pressure strategy for high miles + high fuel economy when using highway rib tires of the highest quality.

Trailer towing sort of comes down to RR tire traction (in a very rough understanding).

The load carried by the truck when towing (trailer tongue weight properly distributed; a 1,100-lb TW expected) will have new individual wheel weights taken, and the truck bed payload shifted around to reflect best compromise of FF/RR and Port/Starboard balance versus accessibility. Pressure readings will be regular as WD hitch adjustments (and scale readings) will be necessary to get the TT payload also "equalled" on all four tires (or six, depending on purchase). This may change the TW somewhat, so the truck will have a an expected small range of tire pressure changes to reflect load or conditions. (TT tires are kept at a constant sidewall maximum).

I've updated my Fuel Log, but it is not so detailed as I was topping off every week (hurricane season) and feeling under pressure during my limited time off (oilfield trucking). Looks as though my short trip (mainly to work and back, about 12-14 miles depending on route) is at 18.5/mpg to be conservative.

I've purchased a 120V 125-psi/3-GL CRAFTSMAN air compressor to keep up with my ten tires (truck & trailer; possibly twelve tires). Fast, fast, fast on pressure changes with all these 80-psi tires! I've recently run the FF tires to 55-psi to see how it "feels" overall. A higher quality 100-psi air pressure gauge will be added to the toolbox.

Other changes, below.

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Continued Update
 

My next day off will see me collecting a number of items for the truck which should have arrived at my mailbox. First among them is a new set of "Towing Mirrors". The "head" is considerably larger with slide-out versus flip-up positioning for towing.

First, a pic of the OEM Towing Mirrors (which are to be replaced):

http://www.monsterautoparts.com/DODG...irror%20R=.jpg

https://www.dodgeparts.com/images/1%20tow.JPG

And the replacement CIPA

http://www.carid.com/images/brand/ci...1_20101213.jpg

http://www.supermotors.net/getfile/7...irrors-005.jpg

The OEM towing mirrors are great when solo. And, I don't think too terrible at mpg (versus -- in the words of BigDave -- the human-infant sized FORD & CHEVY pieces. Or, baby-on-a-stick, ha!). Up, however, the DODGE pieces are probably not so "aero" . . . but the real problem is FOV (field-of-view).

One needs, at all times, to have the trailer rear bumper in view and then beyond. My rig has been at 63' of the state maximum 65' limit. So a rearview mirror which is tall can be adjusted to take in the entire side view of the TT with some adjustment for distance (one is always concerned about turns: potholes, ditches and other obstacles as the two vehicles do not track each other in turns, not even in highway curves). The OEM pieces are fine for keeping the TT in the lane or out of the bar ditch.

But not so much for relative points of comparison. They're narrow, and the FOV at a distance is diminished. Wider is wanted to know what is happening waaay back there. (Remember that one does not have an interior rear view mirror which otherwise serves this function . . the opposing sides of the trailer may as well be in different states).

I'm sorry to say that the majority of towed RV's one sees are handicapped by vehicles with poor mirrors (yes, the law addresses this, but not enough citations to raise awareness), and even more by drivers not accustomed to using them (include yourself, to be fair). Worst are the ones with stock mirrors -- who, because they can sorta see the ends of the trailer -- are actually blind to what is behind and around them. Check the mirrors that they have as you are behind/next to them, please. If you can't see them in their mirrors, they can't see you. Some won't ever see you just due to the component. (And as our economy continues it's inexorable retraction, expect that your fellow citizens will hang onto their upside-down mortgaged house until too late . . and mirrors on an overloaded trailer-towing family vehicle -- the Joads -- won't be addressed when there is no money for such. Be prudent about this already -present future as you roll the highways . . and I needn't mention hurricane evacuations, etc).

In for watching other traffic, especially in metro areas with several lanes and the usual brain-dead, jesus-phone-texting 'muricans barely cognizant of what is around them -- or, ahead of them -- there is, out there, the sad idea that being behind a big truck (or RV) is slow . . and that the solution is to get ahead of it (same lane). That this is dangerous never enters pea-sized brains. I see it daily in big trucks. (This includes drafting and less than four seconds of separation, EM'ers).

Thus a wider FOV, rearwards, yes. But the addition of a properly-sized convex spot mirror adds this (given only as example, ignore numbers):

http://g-ecx.images-amazon.com/image....tow.01.lg.jpg

The small convex mirrors trade depth for range. And the smaller that spot mirror, the worse it is.

When one is piloting a combination rig, the need to know not only what is behind one (as that is often the future) but what is next to one -- or what is about to be next to one -- is critical for best defensive driving. One may need to change lanes for any of a variety of reasons (choosing the path of least traffic resistance high among them).

FE while towing is about the least amount of driver input to maintain lane-centeredness under all circumstances. Predicting the future is part of that. Most RV accidents are written up to driver error. And the error is "loss-of-control" (doesn't matter who's at fault, either). Knowing what is around one (disciplined scanning) is basic: Smooth, error-free, no-wasted-motion driving is at the center of towing FE (subsequent to safest practice).

So I'll be experimenting with 5" or 8" convex spot mirrors on sliding mounts on those two arms. I've no idea past wood blocks carved to accommodate this plan thus far. And, looks like my FE will take a hit, but other changes are in store to help offset this.

.

As always, safety above all else. I doubt the mirror difference will show above the "noise" of measurements.
If you like those CIPAs, I am sure you can get $150 for your OEMS back if you wish. I installed 3rd gen knockoffs on my truck and like them.

Yes, the OEM's will be sold. I expect to re-coup most of the discounted price on the new ones (yay!). As to FE: the OEM ones -- when down -- present a solid, smooth piece. The CIPAs have those two arms -- even when retracted -- and a bigger, flatter head. I'm guessing .5/mpg at 65-mph and under (minimum).

I think not while towing. Maybe as a bare truck, but the trailer hit will make that measurement unlikely.
I shot you a PM on other matters, BTW.

Looking at the mirrors now mounted my initial thoughts on how to mount a 6" convex will have to be changed. The arms describe a V-shape from above, thus putting an arm-mount convex "behind" the mirror head (plane). Am considering mounting to the A-pillar, slightly above the mirror arms, and then rearwards. Getting nasty from an aero point of view, unfortunately. Wont' be solving this right away.

New Travel Trailer
 

Made [2] round trips north to just west of Ft. Worth to buy a new-to-me 35' 1990 SILVER STREAK Sterling travel trailer [TT] to replace the '76 32' I have at present. Had to work around both Xmas & New Years (bank & state offices) thus two trips. I was a little surprised at not being able to get some service done prior to turning south, but, as a test of "worst" there is nowhere to go but up so far as mechanical baseline is concerned, for:

1] TT axle alignment (rear off by 1/2-degree plus worn parts).
2] Brake controller failed, so tow vehicle [TV] had to do all the work.
3] No weight distribution hitch [WDH] attached, so all tongue weight [TW] was on TV rear axle [RA].
[4] Truck is in need of some work.

In short, how not to do it. And holiday traffic on IH-35. A long slow drive carefully near (but not next to) the outer white line. 40-years experience is nice to have (and the years as a pro driver), but it was still a long, long day of keeping the TT tail from swinging inadvertantly.

Freezing temps in northern Texas up to about 60F in South Texas (430-miles), at 57-mph. Coolant temps ran around 188-194F the whole trip (grille block removed for towing portion). Still, saw 14.9-mpg on that southbound leg. Would have been just above 15 had I refilled prior to hitting Corpus Christi versus a couple of cold starts a day or so later.

Pics when I get a camera.

MPG on the initial northbound leg on IH-35 where a solid 23-mpg was seen (grille block in place) at 57-mph/1,750-rpm. Returned via US-281 50-miles to the west (hilly, rolling two-lane), but the yuppies who've moved into the country-side west of Austin ruined that for steady mpg (treating a country highway like a commuter freeway: dense-headed drivers unaware of others); a far sight different than when I used that road to travel to college back in the late 1970's and the relative cost of gasoline was even higher than today. 22-mpg

The second northbound leg was at just below 1,900-rpm (the likely "high" for reasonable mpg) at 63-mph on IH-35 and mpg was 25.

The overall was 2,190-miles at 21-mpg. At $3.90/gl (102-gls; or, $400) the fuel cost per mile was 18-cpm which is on track per history, overall. Fuel use prediction is key to my ecomodder interest: changes to the baseline mpg as percentage increases where expressed as cpm.

Truck solo weight was:

CAT Scale

FA = 4,220-lbs
RA = 3,760-lbs
TTL = 7,980-lbs

With TT:

FA: 3,820-lbs
RA: 5,340-lbs
TT: 6,540-lbs
TTL: 15,700-lbs

As you can see, the TV "lost" 400-lbs off the FA while adding 1,580-lbs to the RA. The TT was nose-down and the TV just slightly nose-up (hitch height was low). A WDH "restores" the FA to the solo value while also transfering some the TW rearwards back onto the TT axles. This improves braking & handling in all respects when done correctly (using a certified three-pad weight scale to leverage per derived values). This is a direct and indirect help to mpg.

The approximate TW of 1,180-lbs is high due to TT nose-down attitude, but will still be in excess of 1k. On an empty TT like this, a 12.5% TW would have been around 820-lbs. With a TT GVWR of 9k -- and an estimating GVW of .92 -- for calculating/planning purposes the TT may weigh around 8,280-lbs once loaded/outfitted. An estimated TW of 13% = 1,075-lb. Close to the actual number above.

Thus, when the TV FA is "restored" via leverage we'd expect to see about 800-lbs on the TV RA and 270-lbs added to the TT axles once the WD is set properly (versus all 1,070-lbs on the TV RA plus 400-lbs from the TV FA). This preserves over 1,400-lbs of TV payload capacity as well (which will be needed with the addition of a larger fuel tank and greater load in bed, as planned).

I should like to see 17-mpg once TV & TT have a better mechanical baseline and TV sees a few improvements as well. This would be low-altitude, level Interstate at under 60-mph. A range of 15-17 mpg would be consistent, overall, with at least a dozen others pulling aerodynamic, all-aluminum TT's of 28-34' at 8-11k with DODGE CTDS (pre-2008) at around 14-16/mpg.

This will be a near-to-the-legal-limit 65' combination rig weighing above 17,000-lbs.

(Current sig pic below shows the first of the three Silver Streak TT's I've owned; that one was a 34'. Appearance of the latest is quite different: radius curves, etc).

.

thanks Slowmover I will use your set up info/advise as a baseline for my trailer when purchased . I am pleased to see the tow mpg numbers as well

We are full timing now too, glad to see mpg's can be so good. Been watching this thread we are going from NC to Fla in a few weeks.

I'll help as I can, fellas. Thanks

Mechanical baseline on both vehicles needs to be top-notch and the proper weight distribution hitch needs to be set up on a certified scale. This is basic, and minimum (and fewer than 10% of all RV'ers do it).

My towing average thus far is 25-cpm assuming $4/gl diesel. That's a more accurate way of looking at tow or solo miles than mpg figures.

Solo has been 15-cpm.

My previous combined figure was 20-cpm . . so the above, at 18-cpm, it is in the ballpark at the start.

.

Towing I have been getting from 10-11.5 mpg. But I usually drive around 65 mph because if I don't the transmission wants to downshift out of overdrive on the rolling hills. On flat ground I can go 58-60 without issues.

aren't you suppose to drive with the OD off to save the trans while towing

I tow with the OD on unless the hills get too long and the transmission shifts in and out of overdrive. Fuel mileage wise I get better with the OD on than off at 60 ish.

MOPAR Winter Front Part #82208646
 

Received the above part via USPS the other day. Just now installed it. A nicer piece than the one from aftermarket supplier GENO'S GARAGE (whom I otherwise highly recommend). Left three of four flaps open for our "winter season" of around ten days (temps stay below 60F in all instances). The next six days is just going back & forth to work. The grille block was removed during the towing trip south (above) and not reinstalled.

Temps going to work (7-miles) get up to 160F pretty easily with ambient of around 60F. Op-temp is 188.6F. We'll see how this piece works as temps are now low 40F, high 50F daily for this week. When I keep the block heater plugged in for around 2-3 hours, the engine coolant will come up about 50-60F from ambient. So, I expect to hit the op-temp mark on the way to work (any hour of 24) and look forward to how it does on the return.

All of this is something of "just an experiment". I expect to move north in the next year or so, so am having fun establishing a baseline for use where the temps are marginal for such.

http://www.dieseltruckresource.com/p...1image0016.JPG


The sides attach with included velcro strips. The top is a combination of clips and velcro. The lower side is clips. The heat exchangers are all of them open to airflow at bottom.

One post by a man from Canada indicated that it was his opinion that the open bottom allowed for "cooling" to some degree. My experience with big trucks is about the same. Keep the fan area open in all but the coldest temps and that -- plus open bottom -- will keep things okay.

My end of it will be the next time I am off and going out on my errands round. If temps permit, we'll see how far under what temps this device is workable waaaay down south.

How far north are you expecting to move?

Denver, CO is the thinking.

Update
 

Time to bring this up to date.

I use the winter front a few weeks of the year, and the four piece grille block the rest of the year when solo. A/C season means no block at all. Temps come up faster and are more consistent with the block. This means those three gallons of engine oil come up to temp faster.

I've added a rear antiroll bar where none was present on this 2WD IFS truck, and changed the front bar to a larger size. A Panhard Rod is on the list.

Today the truck tools around at just under 8k lbs for normal load. About 1200-lbs of bed topper and gear as in above weights.

Divorced since 2012, I set up my usual errands to occur in one part of town. And other services or suppliers are near or on the route to and from.

I don't pay too much attention to FE, but have kept new habits. Usually see around 19-mpg in the city limits.

Recently ran a 1,025-mile round trip out to West Texas for a job, and saw 25-mpg overall. 62-mph.

Sure do like 10-cpm highway!!!

Plan to move about seven hundred miles with travel trailer in tow. Am expecting to be near 17,000-lbs combined, in a 63' long rig. 14-16 mpg has been the usual range. Am going to shoot for higher if the stars align and I can attend to some mechanical details.

This site a great place to keep on track with reduced operational expenses. Where to spend for where it counts.

Getting ready to make a 440-mile run with the 35' Silver Streak in tow. Referring to Post #7 of this thread I'll be traveling at 1600-rpm give-or-take which with the factory gearing is approximately 54-mph.

Some local freeway runs at this rpm show (round trip) the truck settling in at 27-mpg (28.5 uncorrected).

The trip will start at around 2200 Saturday and end near 0600 Sunday morning. Avoiding that killer IH35 traffic north to near Fort Worth.

I've not been able to finish the list of mechanical entails to optimize mpg, but have done a wheel bearing and brake adjust on the trailer. The hitch setting will be roughed-in, and I may decide to get a scale ticket or two. Etc.

Planning to stop twice, with maybe a third.

The combo has hit 15+ in the past.

At the lower speed (and hopefully no winds) 16.2-mpg would be a 40% towing penalty. 30% (the future goal) would be 18.9-mpg.

I'll be excited if I can hit 17-mpg (corrected) for long stretches. The ton mile calculation should be impressive.

Looking forward to correcting the fuel CPM for towing in my sig from the current 17-cpm as prices have dropped as well.

I'll be looking at engine run time to see the actual travel speed. Google estimates 6' 45" for a solo vehicle, or about 65-mph.

Love it, driving at night to miss that traffic. you've loaded the dice in your favor as best you can.
I had the opposite week of commuting.

Great to use Google maps to plan stops. Never easy to park 64'.

Left town and was at 13+ up to fuel stop at mile 56. Readjusted hitch now on paved level ground and found a full mpg. Steadily climbed past indicated 15 thru Austin at 0245.

Arrived at Weatherford at a solid 15-mpg. Trailer axles out of alignment, so was dog legged the whole way. That's with being only 1/4" out plus wear.

Really need to drop truck gearing to 3.42 from 3.73. This 9k trailer is simply no challenge. Even future routes thru mountains will just give the diesel a needed workout.

Trailer axle alignment, rebuild truck front end, and higher gearing can take me to that 17-mpg desired under best circumstances (so I presently believe).

Higher than that will take more work. I'd sure like to see 18 on a regular basis as that is a common number for the 4WD crowd running the highway solo.

Impressive level of detail subscribed just got a personal best of 3.61g/100mi 100mi no aero mods 8mi costing engine on the rest cc set to 55mph.no EOC I crested Bolder hill pass Summit @55mph 825egt and went to neutral egt was 500°f for the first 1.5 mi slowly droping EOC would kill my turbocharger in no time as the egt will rise to match the glowing 800°f exhaust manifold and turbine housing from pulling 800EGT for 4+ mi . Plus an automatic transmission @ 85+mph and EOC for 4mi ×3 passes each200mi round-trip to the VA = trans failure...
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Slowmover do you have an EGT gage if so do you notice a coalition betweenEGT and psi boost. I run a fast responce k-type thermocouple moves as fast as a tachometer sinitve enough to Sinise the ac compressor's 25°f load at idle and 50°f for being in gear.
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Duse your trans use a TV cable (Throttle Valve)if so try adjusting it . My 91 D-250 took 4 notches to pull the pass in OD@55mph. Now it downshifts @850°f EGT instead
of 650°f. I can hold 55mph in the flats @500°EGT compared to 650 EGT @65mph I need to get a trans temp gage befor tomany 55mph passes
Gumby stay flexible

Slowmover has a 6 speed manual, no TV cable.

And no ET gauge. Or, Manifold Pressure. Yet.

My driving is pretty much set the cruise control except in hilly terrain. Towing, I'm more likely to downshift early. Same for winding out the motor once past Third also when towing.

Otherwise am concious of slowing early for planned stops from highwAy speeds. No last minute decisions.