Big Diesel, MPG increase ideas?

[ps2fixer]

Fixed half of the glow plugs (driver's side). Had 1 bad, 1 with no connection. Other 2 worked but replaced anyway with new. Didn't have the 8th one so didn't do passenger side yet. Block heater cord came today as well as the massive upgrade solenoid for the glow plugs.

I got to use the truck as a truck on Sunday, 220 miles to pickup another f250 diesel for parts for my dad. Paid $1050 for it, not too bad for a nearly complete truck (top of cab cut off). 220 loaded miles and could barely tell the truck was back there, just started out in first instead of 2nd (no throttle needed still) and big hills I had to down shift for at 60mph. Drove 60mph to and back on the express way except on the way home there was a section of really bad ice for about 5 miles that I went around 30-35mph. Truck was hauled backwards on a dolly, so not really ideal for mpg. Anyway, filled the tanks today and did the math.... 23.66mpg, not bad! There's only 4 active people with diesel trucks, but I'm currently at #2, #1 sounds to be a really small truck. Wish I had instant feedback for mpg, the scan gauge xgauges worked well, but it couldn't calculate the mpg sadly. Truck seems to run better the more I drive it, that or I'm just getting used to it.

I have new fluids coming for it, almost $200 to replace everything with synthetic and I still have to grab the engine oil which will be another around $100. Not 100% sure how I really want to go for long term with oil since it has the HEUI system the engine oil needs to be kept top notch or they could get sticky or build up material inside the injectors.

Overall, I'm quite happy with the manual gearing with 3.55 axles, good mpg for long trips, yet plenty of low gear for working with loads. Get things 100% with the turbo and it should have more power at lower rpm. The scan gauge shows I get nearly no boost till I hit 2000rpm+. At 60mph 5th gear I'm seeing roughly 2psi of boost, on a hill it jumps to 3-4psi. Heavy take off and high rpm (over 3000rpm) I think we saw about 14psi, but at those levels the flow is so great the leak isn't as noticeable I'm sure.

Kind of funny my target was 25mpg and I got really close to that in winter with a boost leak, and about 1/3 the tank was loaded miles, also still have 2 bad glow plugs for the cold starts and no block heater. With the results I see, on longer trips with some areo mods I think I could hit 30mpg somewhat easily. Oh, also the front tank wasn't 100% full for the last fill up so the mpg should be slightly better than the reported number. Both tanks this time are completely full so the next fill up should be a lot more accurate.

Truck still has a vibration at 45mph, have to diag exactly what it is since most of the U-joints are replaced. Have one in the rear drive shaft that wasn't changed (right on transfer case), and the front axle u joints aren't good but truck is in 2wd and hubs unlocked so it shouldn't be turning ideally but very well possible that's the cause of it.

This is making me want to swap my car over to a small diesel, maybe a small diesel pickup. I suspect something like a Toyota Tacoma with a 1.9L TDI VW engine could hit 40mpg pretty easily, maybe 50mpg with me behind the wheel.

We didn't throw the tuner on the truck for the trip, my dad thought about it but I figured with the boost leak it wouldn't help and probably just waste fuel. Now I'm wondering if the tune would help the mpg. Generally the first or second setting up from stock gives the best mpg, atleast for the automatic trucks. My dad's went from like 15mpg to around 18mpg and he wasn't driving his truck for mpg at all back then with 4.10 gearing.

Anyway, I was hoping to hit around 20mpg before fixing the truck up 100%, hopefully I can squeeze out a bit more with the new fluids and get some basic eco mods done.

I haven't searched it out, but I wonder if there's a way to get the scan gauge to be happy with these trucks to give an instant mpg readout (or any kind of fuel over time type of measurement). Worst case I could build something on my laptop and use it for data logging and such, but ideally would be to use the smaller scan gauge.


I scanned over some ecomodder truck owners in the garage section of the site. Any of them that were getting around 18mpg+ were manual diesels for f250 and f350. The highest average truck I see is around 27mpg, next best is low 20's. The 27mpg truck has pretty extreme mods done to it including an external overdrive unit (double overdrive) and a lot of areo etc mods. I'm sure it will be a solid fight to try to get 30mpg within my limits (no lowering the truck etc). Pretty interesting to see I'm performing pretty well as purely a driver and no real mods on the truck besides the bumper if you wanted to call that a mod.

[squirrl22]

Couple things- congrats to going thru and getting everything fixed. That's step #1.
One thing that can help is getting your injectors cleaned, rebuilt, and balanced-After 190k, they may be pretty worn.

A proper tune- one for economy, not for power- can make a big difference.

Reading thru other's experiences is invaluable- Here is a web site that can help in your quest: https://forums.tdiclub.com/index.php...el-economy.24/

Consider running highly filtered(below 1 micron) used transmission oil , either mixed w diesel , or you can run it straight, in tank #2. It's an old diesel trick, actually cleans and lubes your entire fuel system. You only switch to tank #2 when the engine is at full operating temperature.

Consider putting in the hottest thermostat you can find. Diesel's love heat.

[ps2fixer]

Good tips, my dad did the transmission fluid (new) on the 2001 parts truck when we first got it going. Haven't changed the fuel filter on my truck yet, but when it's replaced that's the plan too.

I don't have a thermostat readout for my scangauge, but the engine oil temp showed 203F while driving 60mph, peak of about 214F while towing up a large hill.

I'm still fixing things slowly, parts are slow to come and the work area has been tied up with other vehicles quite a bit lately. I have to truck at my house atm, just fixed the marker lights (1 busted, 1 burnt bulb). I also have a front market light that has the lens with a small hole in it.

I found suggested shift points for the diesel in the owner's manual (diesel supplement), wow I was really over reving it according to their figures. I was shifting into 5th at around 50mph, all the other shifts were based on rpm @2k. I'll have to see what kind of rpm the shifts are at. Same book also suggests idling for 5-7 mins after a long trip to cool the engine, but only 15 seconds after starting a cold engine before taking off. It basically says to wait for oil pressure to rise to normal range. The book doesn't say what year it's for, but clearly it's for a 99+ truck. Looked at the axle ratios in the book, it doesn't even list a 3.55 as an option. I guess I got the highest gearing possible for a factory f250 with the diesel.



Sadly the owner's manual has no wire diagram info. I personally believe service data (wire diagrams etc) should be available free for anyone that owns a given product. If I can't find a solid source for the data, I can buy limited access to the wire diagrams ford dealers use. I read there were a couple sites that hosted pdf files of the cd and dvd's but haven't found a source for them yet.

The 92 my dad just bought doesn't display mileage on the odometer, it was sold as a 130k mile truck, but it would be nice to validate it. I'm guessing it's a power source problem or similar. I'd hate to poke around it blindly with out knowing the pin out for the connectors.

Anyway, kind of funny the TDI site is suggested, I was just telling my dad a day or two ago that we effectively have TDI's, just the engines weren't marketed that way. Similar to how our car's are DOHC but never were marketed that way.

Since I have a way to monitor engine temps somewhat well (oil temp), I can block off the grill more until I either see temp rises, or it's completely blocked off. In cold weather I'm pretty sure it's just fine being blocked off, just not sure about summer time driving.

I'm thinking about toying around with the tuner stuff, but figured it would be best to get some base line figures before jumping into that can of worms. My current 23.66mpg figure is only one tank and includes 2/3 being used in one day. My normal usage will be a lot more shorter trips, atleast while I'm driving the truck more often to get used to it and such.


EDIT:

Took the truck for a quick drive (still warm from doing some work on it and keeping the batteries topped off). Every gear shift suggested in the manual for best mpg is around 1500rpm, 2nd into 3rd is around 1900rpm (bigger jump in gearing). I'll have to target the 1500rpm shift and ~2000 rpm shift for 2nd into 3rd to see if I get good results. The truck seems fairly happy with those shift points, I think when I was testing before the shift I watched the most was 2nd into 3rd which is the big jump and 1500 is too low for that shift.

[Isaac Zachary]

Originally Posted by ps2fixer

I found suggested shift points for the diesel in the owner's manual (diesel supplement), wow I was really over reving it according to their figures. I was shifting into 5th at around 50mph, all the other shifts were based on rpm @2k. I'll have to see what kind of rpm the shifts are at. Same book also suggests idling for 5-7 mins after a long trip to cool the engine, but only 15 seconds after starting a cold engine before taking off. It basically says to wait for oil pressure to rise to normal range. The book doesn't say what year it's for, but clearly it's for a 99+ truck. Looked at the axle ratios in the book, it doesn't even list a 3.55 as an option. I guess I got the highest gearing possible for a factory f250 with the diesel.




EDIT:

Took the truck for a quick drive (still warm from doing some work on it and keeping the batteries topped off). Every gear shift suggested in the manual for best mpg is around 1500rpm, 2nd into 3rd is around 1900rpm (bigger jump in gearing). I'll have to target the 1500rpm shift and ~2000 rpm shift for 2nd into 3rd to see if I get good results. The truck seems fairly happy with those shift points, I think when I was testing before the shift I watched the most was 2nd into 3rd which is the big jump and 1500 is too low for that shift.

Sounds about right to me!

[squirrl22]

Following the owner's manual is CRITICAL. Glad you found one, even if it is not the right year. Make sure you allow for proper cool down 5-7 min sounds abt right- esp if you have been towing.

I've had great success with buying my parts from Rockauto. - excellent prices, excellent parts. They have OEM grade thermostats starting at $6.

Seriously, check into supplementing your fuel with used ATF. I worked out a deal with a couple quick oil change places, - they often have to pay to have it hauled away.

[Piotrsko]

Since we are talking thermostat: the FTE forum noticed a hotter (215?) degree setting made easily noticeable performance and efficiency improvements and there are kits to change over.

Should be able to see the stored odometer reading in Forscan or Torque pro, I just don't know the PID request statement.

If you're going to run used trany oil, you will need an extra filter that does at least 1/2 micron otherwise you will fubar the injectors.

The owners manual is for people who never owned or drove a diesel and generates a overly conservative method of operation that normally would not break things. Proper ecomodding is so far beyond that.

Finally: consensus is: anything over 2000 rpm is a waste of fuel

[ps2fixer]

Yea a lot of forums said keep the rpm under 2000, was like the universal suggestion lol. 70mph is right around 2000 rpm and 55mpg is right at 1500rpm. 60mph should be around 1700rpm which seems to be a pretty solid sweat spot for this engine.

According to this site, the peak torque is around 2000 rpm and looks like 1700-2200rpm is a pretty solid area to try to stay in for torque output. Almost makes me think going 55mph might actually hinder mpg slightly vs 60mph, atleast with a mild load. I guess I hit roughly the ideal rpm range with out really knowing. My first thought was 55mph on the expressway, but figured the 5mph faster would be worth it for the long trip.

7.3L Power Stroke Diesel Specs & Info

Also really interesting the IDI peak torque is at 1400 rpm. People always say how bad the MPG is with the IDI engines, but I bet they are running them way too high of rpm. Based on the chart, I'd guess 1400-1800rpm would be ideal for the IDI engines. I guess that still falls under the under 2k rpm suggestion xD.

A hotter thermostat might be a good idea, my engine oil seemed to hold a pretty cool temp, not sure how hot is too hot though. Online is saying targeting 250f or lower is best and around 275 is when the oil starts to break down. I saw around 214 peak on my trip with a small load so could probably bump the water temp up a bit (thermostat). I know the diesel likes it more, but trying to keep in mind the other fluids, wiring, connectors etc. It's crazy how trashed harnesses are from vehicles in hotter areas of the country, here they might get a little stiff but in the major sun in like AZ or FL the harnesses can get so hard any flexing breaks the insulation. I assume that's from higher average temps and hotter under hood temps.

The owner's manual has a lot of good suggestions, but it's always very conservative on most things because of possible lawsuits and such. I might not be a diesel expert, but I've worked on vehicles and engines since I was about 10, same story with my dad (he did it professionally). I just turned more to electronics and computers for schooling, got my dream job, got bored after 4 years (midnights at a large corp) and moved on. Anyway, I've always learned to ask why instead of blindly following ideas/things. So I'm really wondering, why is it suggested to idle a diesel to cool it down vs just turning the engine off and letting it air cool? I'm sure there's a LOT of people that don't follow that suggestion and never heard of really any engine issues with these engines. Generally in parking lots and my road/driveway I'm idling for 2 or so mins even though I'm moving still so I'm naturally getting some of the cooling effect with out trying. Is there a target temp to try to hit, I don't really have a coolant reading (yet), but I can watch engine oil temps. Next time I drive it far enough to hit max oil temps, I'll have to let it idle and see what it drops to.

I'd assume the suggestions for the other diesel trucks would be similar, the ford one says to not pull start or roll start in gear as it damages the cat. My truck doesn't have one since it's the older model, but I'm sure the newer diesels have it. If that's the case, then engine off coasting and restarting with the momentum of the truck is a no go to the manual. If the engine rpm goes high enough, it should be the same thing as using the starter.

It seems like some of the best mpg tactics are a compromise, like going around corners faster but still safely adds wear to bearing and tires, but the fuel saved in theory would be greater.

With the power stroke, not really planning used oil or trans fluid, atleast haven't thought about it too much. The IDI engine would be pretty ideal for that kind of setup since I'm sure the injector nozzles are larger since it runs a lower injection pressure and also is ran through a mechanical injector pump. I'm not against a mix in summer though, like I was planning to research what grade of filters and build atleast some sort of simple setup (bucket + gravity feed through the filter or whatever) to filter the used engine oil from the truck to dump in the tank. I was thinking like 5-10%. On the old VW diesel engines (like 80's era) it's known that will run on vegi oil and similar by just preheating the fuel. I've seen a few videos on it, they generally run the car on diesel to warm it up, then switch to the vegi oil and before turning it off they switch back to diesel to purge the system for the next cold start. I know where 55gal is that I could probably get free, but it's from a restaurant that served beef products and other meats so the oil has animal fats in it. The guy was trying to make his own biodiesel but ran into issues because he didn't account for that. I think he ran on the stuff going home (he's from way up north of me). Used engine oil and trans fluid seems more logical since there's a ton of the stuff, but I also live in an area that gets cold winters and people burn the stuff for heat sometimes. It seems to value around $0.50-$1 per gal, but free might be possible from a business.

Anyway, I should mess around with some areo mods before long. I can't do the belly pan until all the fluids are set. I probably need some axle seals and such too and I think one hub had some grease on it so it's seal is probably junk too. Plan is fix the leaks, change the fluids to some really good synthetic stuff and figure out a belly pan/skid plate setup. Clearly can't do much about the axles, but figured the rest I could do something about. I plan to undercoat the truck then add the belly pan with the idea that the salt/water should hit the belly pan mainly and likely not wash off the undercoating. Probably still be a yearly inspection on the undercoating and such, so I need to make the panels removable. I'm thinking of making it of metal since this truck isn't exactly light and bottoming out would destroy just about anything else. Current idea is some flat bar (maybe small square tubing) for the basic frame/shape and thin gauged sheet metal to skin it. Primer, paint, then undercoat the belly pan too. Might be a bit of a mess to take off, but it shouldn't rust out. I used coroplast on my corolla for a 1/2 engine bay belly pan and it did work out pretty well, but the distances where real short and I had a center support to rivet it to. I'm thinking front will be a standard skid plate with thicker metal, center could probably be plastic or light metal and same with the rear. I've thought about the front end as well, I could run an air dam below the bumper as long as it's flexible and would hold up to steep drive ways (common in my area). First thing that comes to mind is conveyor belt, but it's heavy. Landscaping plastic trim would probably work for ~4in of drop.

I went pretty crazy on my corolla, sealed the hood, covered up most of the front end, sealed around headlights, etc and most of it I saw effectively no gain. Passenger mirror delete was a bigger gain than sealing up the front end. With this truck being a brick, I wonder if it would help much sealing around headlights and such, or focus on other areas (mainly the bottom). Next biggest loss is probably the topper, but it seems to be working out pretty well as is for now. I'm sure with out the topper I'd be getting worse mpg based on what I read online for other people's mpg at slower speeds on the express way. Best I saw was something like 19mpg going 65-70mph with 3.55 gearing.

Anyway, I'll have to poke around the forums for some people with experience running used engine oil/trans fluid in these engines. I don't drive a lot, but when I go on longer trips it would be nice to burn cheaper fuel =).

[Piotrsko]

Well the idle after a run thing is an old standby on 7.3 international schoolbusses and the oiling/bearing system of the garrett gp38 turbocharger. If you come in without a 5minute cooldown, the bearings eventually coke solid and the lady drivers whine about being gutless. In 20 years, 25 mph driving between the freeway and house after a good pull was enough cooldown.
The other thing is: below 30, mine never opens the thermostat with cabin heat on max . The approved winterfront I saw had an opening of about 1sq ft.

Mine is known to be able to run veggie oil straight in the summer, too viscous in the winter, 50/50 is optimal, no issues.

Pretty sure it wont EOC without killing power to the IDH. Mine will give it full fuel to keep idle going, great clutch trainer.

Keep saying mine because there's a lot of changes between 95 and 2003. Many changes between 99.5 and 2003.

[Isaac Zachary]

The way I look at my manually shifted vehicles is that I control the acceleration via the shifter, not the pedal. The pedal needs to be as close to full throttle as possible, especially in a diesel. As long as I'm not going under idle speeds I upshift whenever I don't need more acceleration and downshift if I need more acceleration.

Granted I've mostly driven diesel vehicles with very low power to weight ratios. A sort of disadvantage to a turbo-diesel pickup is that for most scenarios they are overpowered. I drove my brother's Dodge Ram and felt like I was riding a bicycle.

Vroom!-clutch-Vroom!-clutch-Vroom!-clutch-Vroom!-clutch-Vroom!

I was also in top gear after about 40mph.

[Piotrsko]

Well I like to say any foward gear is acceptable to start off in. Do have to slip the clutch a wee bit in 6 th. And actual 1st is great in LA freeway rush hour, never go fast enough to shift up never have to put in the clutch