11 mpg to 15 mpg is it possible mostly on driving style and small mods?

[Milwaukee]

First

Get vacuum gauge. and turn off overdrive until you go over 50 mph if you have 3.55 gear.


I have 96 E350 passenger van it weight 9,000 pounds. 5.8L with E40D.

gear ratio was 3.55

Most time I get 13 mpg in city and 17 mpg on highway load with 15 people.


When I didn't have vacuum gauge I got 9 mpg in city and 12 mpg on highway.

Keep vacuum gauge pressure about 10 or high is best.

Make sure 4wd hub lock out are disengage correct. Most time they get old and stuck which cause 4wd work all times until you notice mpg terrible.


You wouldn't see 12 mpg or high due you fill gas tank per month which gas can disappear. Example you have 5 gallons of gas but 1 month it 3-4 gallons due leak fuel cap or leaky tank.

[Frank Lee]

Why turn off OD?

I lift at 42mph to kick it in sooner.

[Milwaukee]

Not for 5.8L with 3.55. But for diesel Yes.

When it kick overdrive in 40 mph and vacuum gauge drop FAST. like it should be 10 or high to get great mpg when overdrive kick too early it went to 0-2 which is bad plus it lug engine.



I put 10,000 miles on van so I know how it work. I try with overdrive under 45 mpg and didn't get 13 mpg it was 9-10 mpg plus it get little Hotter than normal.

[rmay635703]

Originally Posted by Frank Lee

Why turn off OD?

I lift at 42mph to kick it in sooner.

My dodge is like that also, there are many circumstances when I get better in 3rd than 4th because there is so much slop going on sub 48mph especially if I have to press on the pedal at all, usually I can't maintain speed without massive FE hits in 4th if there is wind, hills or a reason to accelerate. If I end up in 4th around 40-50mph I keep my fe high or even coast loose speed and speed up again as opposed to trying to accelerate in 4th, manual downshifts seem to result in a bump in my fuel usage for some reason (even with my foot off the pedal)

Strange how automagics are setup, I really can't understand what the purpose of many of the behaviors I encounter on the scanguage are, especially the coasting downhill with foot on pedal to maintain speed then FE drops from what it was on flat ground while going DOWNHILL!

Bleh, I really am starting to dislike automatics

[bgd73]

Originally Posted by JacobAziza

I have an advantage in that I have a diesel, a manual trans (but no overdrive), and a standard cab.
My starting mileage is the same as your goal.

But with relatively minor changes I brought my 1983 F-250 from 15mpg up to 25mpg average with mixed loads up to 3 tons (28+ running empty)

Vehicle efficiency upgrades: 28.5mpg (so far) in 2.5ton commercial truck
Its easier to have big increases when you are starting from such a low number. In a small car +10mpg may only be a 30% improvement, while for you that same 10mpg would be 90% better. 4mpg is totally possible. Ford wasn't trying to make these things fuel efficient in the least, so there is all sort of room for improvement.

I am glad to read this, I knew of the diesel secret since I was a kid.(25 years or more) today, add turbo, and calm it down. wow. I always assumed, as america hurts itself for the capitalist, the diesel trucks into the high twenties raised prices...strangely so, as diesel is easy to get from petroleum.

My truck experience and the same 15 mpg left me scratching my head. I would swear that is a minimum. OE keeps the lean out for heavy hauling. If you are not hauling, get dynamical with the injection, if it means a piggy back computer. Step up ignition if it needs it, and even the oil pump.I have stepped up the carbs into 20s quite easily (3/4 ton 5.7 chevy)...but it pinged in loads. that is when I deciphered the "einstein" of trucks left as oem...they make it run pig rich to last the 5 year pay plan...

I still want a diesel, 1980s suburban style with something modern under the hood.

Is this a repost or am I caught up in a bigger repost?

[JacobAziza]

Only, why would anyone get a big truck if they aren't hauling with it?
My 25mpg is with hauling, and hauling lots of large heavy loads (full apartment worth of furniture and boxes, 3 tons of broken concrete, etc) and it sounds like the thread OP is planning to use the truck as a truck too.
Also, I don't have any computer to play with. Wouldn't upgrade if I could though. Mileage hasn't improved at all in the past 30 years, why bother to have something modern? More complications just means more stuff to break and more expensive to fix.

My original point wasn't about being diesel, but just about these older full size trucks having lots and lots of room for improvement.
He might not take all the exact same steps as I did, but I'm sure he can reach his goal and then some with out spending much and w/o any major mechanical changes.

[strider3700]

I have 4.10 gearing Not sure how that affects things with the overdrive.

It is possible for me to do most of my driving at close to 35 mph or lower but I have to determine is it better to do lots of stop signs/lights or is it better to use the highway and do 55 with a lot fewer stops. With my old truck the highway was better so long as I made certain to keep it between 50 and 55 mph. 65 was enough out of the optimal rpm that I lost close to 30% the truck couldn't do 75 but I'm sure it wouldn't have been better.

Yes I definitely use it as a truck. 75% of it's miles since I got it have had a load in the bed. usually it's full of firewood so far but todays load is grass and dirt heading one way mulch coming back.

Thanks for all the suggestions so far. I'll keep an eye out for a vacuum gauge next time I'm near somewhere that will carry one.

[JacobAziza]

I find here in CA, land of the 12 lane superhighway, people are surprisingly understanding about me driving well below the speed limit, so long as I stay in the slow lanes

I have no overdrive, and I stop the engine at every stoplight, and I still get better mileage on the highway than on the streets...

but you never know, you'll have to try it to find out what works best for your particular vehicle.

[brucepick]

Hi strider3700.

I see you're way up North where it will be cold in winter - and you don't put too many miles on the truck.

So I definitely agree with the person who posted earlier suggesting a block heater. Definitely a good idea. With a block that big you'll need to burn a bunch of fuel to warm it up - and you'll be burning most of that "warmup fuel" in open-loop mode, where the computer has it run rich because it's detected the engine is cold. Prewarming it electrically is way cheaper than doing it with fuel. The shorter your trips are, the more benefit you get from using a block heater. My commute is about an hour so I don't have one.

2nd topic - there's a big plus to running at non-highway speeds, as long as you can coast to stops. You'll find lots of past discussions here on the best way to do it with automatic or standard trans. Main point is, at highway speeds you're constantly fighting the aerodynamic drag which increases dramatically the faster you go. Up to about 40 mph the aero losses are almost insignificant and you can essentially pulse + glide the whole way, using the engine only when you need to increase speed.

With an automatic, you have to read the owners manual section on being towed, to learn what speeds you can coast at safely with the engine off. It varies with different trannies. If the engine is idling in neutral, most trannies will let you coast all you want. With the engine off there may be insufficient fluid flow and/or pressure to keep the tranny healthy, as the wheels are spinning the tranny internals. Of course if you kill it, you'll have to swap in a standard, which would be ideal!

I used to drive a boxy thing with automatic and lousy aero. NOT a Detroit iron beast. I got my Volvo wagon, EPA rated 17/22, up to about 30 mpg commuting on hilly limited access roads, in summer weather. I limited uphill speed to about 50-55, then goosed it after I crested the hill, got it up to about 70, put it in neutral and coasted down the rest of the hill with engine idling, as well as it would coast. Higher tire pressure helps your coasting.

Leave foot off the gas when slipping it back into Drive - that gave me the smoothest "shift". Rev-matching was pointless, it was much better going back into D at idle speed regardless of vehicle speed.

[rmay635703]

Originally Posted by strider3700

I have 4.10 gearing Not sure how that affects things with the overdrive.

It is possible for me to do most of my driving at close to 35 mph or lower but I have to determine is it better to do lots of stop signs/lights or is it better to use the highway and do 55 with a lot fewer stops. With my old truck the highway was better so long as I made certain to keep it between 50 and 55 mph. 65 was enough out of the optimal rpm that I lost close to 30% the truck couldn't do 75 but I'm sure it wouldn't have been better.

Thanks for all the suggestions so far. I'll keep an eye out for a vacuum gauge next time I'm near somewhere that will carry one.

If you don't tow trailers much up your gearing to the 3.5 area and your FE will go up a bit on highway.

Because you have an automatic I can't recommend driving in areas with stop signs. Stop and go in an automatic is VERY difficult to get acceptable FE. On my dodge I have country-ish stop and go with hills and I can get the same as Highway fe by timing my coasting up the hills so I am down to a low enough speed to turn or stop.

Unless you can time your route perfectly in town so you never stop and tolerate coasting down to 12-18mph (normally) every time there is a stop or turn I can't recommend in town over highway. You can try it but it is very critical that you get everything mapped out and timed so you know exactly when to coast, accelerate, etc. One stop from a rather high speed can kill your FE for that entire trip. Different vehicles obviously respond differently to pulse and glide and in town driving, my dodge works OK but I need to glide up and down much more in speed than is normally acceptable and as I said one stop when I shouldn't be seems to kill my FE for the trip.

Good Luck
Ryan