Not all of it is practical, but considering high fuel prices I thought it would be apropriate to start a hypermiler thread to swap ideas on how to stretch every last gallon of fuel.

I'll start off----------

Base vehicle: 1986 F250 diesel C6 auto, 4.10 gears 2wd 9-12 MPG

Mods/tweaks

1) 3.08 gears 13-18 MPG

2) ram air intake 13-20 MPG

3) transmission swap (E4OD) 15-21 MPG

4) turbocharger (peak MPG did not improve, but average was slightly better when loaded)

5) Cruise control mod: reduced the max throttle that the servo can pull to less than 30% power.

6) removed canopy (this alone is usually worth 2 MPG)

7) tailgate up (have not tried with down yet)

All of the above is what yeilded up to 23 MPG. Average cruise speed is 70 MPH for most of my driving.



Driving style----------

I live in BC, and there are a lot of long shallow hills. To that end, modding the cruise control prevents the truck from stubbornly holding on to the exact set speed I selected. In addition, the cruise control is more steady than most of us when it comes to holding a constant speed. Steady fuel settings helps fuel economy. On steeper hills, the truck will lose up to 5 MPH and regain speed on the top. If desending into a valley, I will allow the speed to gently drift up while going downhill and this helps save fuel going back up the other side. There are a few bridges that are low like this.

RPMs. As I observed the following seems to be best for economy:

Empty)

60 MPH 1500-1600 RPM
70 MPH 1600-1800 RPM

Towing)

60 MPH 1800-2000 RPM
70 MPH 2200-2500 RPM

In the case of a tall geared truck where you actually have the option to keep the revs that far down at those speeds, let the EGT gauge be the guide for when to use the taller gears. In general, if the EGTs are not significantly higher in the taller gear, the economy wil be better. If however, going into overdrive results in an increase in EGTs of 200F or more, you are probably using more fuel than in the lower gear. Exahust smoke is a dead give away. Smoke = wasted fuel

Wind and rain can kill MPGs at least as well as my temperment when drivng. For the same speed and trip, 4 MPG drop is not uncommon.

And naturally, keep the tires fully inflated.

 

One thing that you may want to start checking David. The truck I drive at work I have been driving since it was new and it has 36000 miles on it. I have tripped every tank of fuel it has been run through it. We change the oil in all of our trucks at 5000 miles. I have noticed that after the motor gets about 2000 miles, on it the average, fuel mileage drops. At the point I change the oil it has lost, on the average, 2.5 MPG. I change the oil and it goes back up on the next tank.

Now I am trying a different brand of oil and see what it does.

 

I guess thats what synthetic is supposed to correct. But I will keep an eye on that, now that you mentioned it. I have noticed that diesels seem to be more affected by the condition and quality of the oil. I never considered synthetic because it was too expencive and my engine(s) were forever using oil. I am also running a powerstroke oil filter.

 

I talked to another guy that has been doing the same thing. He said, "synthetic didn't seem to matter".

I am due an oil change in about 1500 miles. I will put synthetic in it and see for myself.

 

Got back from another trip loaded this way for both directions:

Unfortunately, I think I overfilled the tanks slightly when I got back. The fuel gauge pegged 1/4 past the "F" mark and It doesn't usually do that. This represents quite a dilema on how to get accurate MPG results because the factory fuel gauge can be so inaccurate. How can I be sure that the tank is filled to the same level each time.

My best guess is that I reached 20 MPG.

I'm thinking of adding a marker in the filler flute of the tank that I can see when I fuel up to verify that there is same amount of fuel in the tank each time I pull out of the cardlock.

For the next trip, I think I will just run on the single tank for both directions to eliminate one of the two possible sources of error. The larger the fillup, the more accurate the result will likely be.

New tires are also on the way and should be on by the time I'm ready for the next trip. Right now, all of my tires are out of ballance and at least two of them are out of round

 

yah i use to get 22 mpg on the interstate before they switched to ulsd and and i also put 33inch mudders on it

 

Care to share some details? speed? current MPG?

 

OK, I've just found a really easy (and cool) way to verify the accuracy of your odometer using google earth.

I noted the distance on my way home and it was 166 KM and change. The address of the paint shop and the cardlock are both registered in the google earth engine so it was a simple matter of using the directions feature. And Boom! done!

Result was 166 km according to google earth. Kind of creepy actually, because they also updated the scan of campbell river, and not only can I see my house now, but I can also see my truck in the back yard

They were way off on the time estimate though. 2h, 53 minutes? LMAO, if it takes me 2 hours I'm going slow
Its not like anyone else follows the speed limit anyway

 

Get you a GPS.

I fill up at, basically, 3 locations and I have put 36K on my service truck so my numbers are probably pretty close.

You are going to have to run several tanks through it do get a good number.

You have airplane gears and OD trans so you will probably get the best or very close to the best on this forum.

 

A GPS will be on order eventually. But for now this leads me to believe that my numbers are close. I got the idea from another website where hypermiling leads to some crazy driving habits, but Google earth is after all made using GPS. Several other guys reported similar odometer results using google earth.

Whats really hard is controling the conditions. Wind at 70 MPH is a killer on fuel economy, and its very rare that I can run the truck this empty. I've only done one trip this year empty enough to have the tailgate up. Normally I'm towing a trailer and that means 15-16 MPG usually (13 when I had the C6).

So far I have two consecutive trips with similar results this year. Next week will be the same conditions, so that will help to validate the current results if I can get the same MPGs. My long term goal has always been to consistently get 20 MPG @ 70 MPH empty.

Last week I ran completely empty half of the trip, and that pushed my average up to 21.5 MPG, calmer wind also helped.

 

Before I had a GPS I would calculate how far off my speedo./odometer was by pacing ten mile markers. Then you can figure out how many percentage points you're off. My Cherokee is 5% slow with 31" tires and so is my Cummins-Dodge with 33". My wife's Suburban is 10% slow with 35" tires. My '90 CrewCab gasser is 10% fast with 36". The '94 IDI turbo is 1/2% slow with stock tires. I calculate my mileage and deduct (in the case of the '90 F-350) or add (for everything else) the appropiate percentage off of or to the figure.
The mile markers might not be exactly perfectly spaced but they're close enough.

 

My M.P.G 1991 F250 ATS turbo best is 20.06---The drive to work, stop & go, plus interstate (about 60%)= 16+ to 17.4... drive to work averaged 3 tanks...

 

If you average enough tanks of fuel, you get very accurate numbers after a while.

Since I use my truck for business I get a cash reciept for all the fuel I buy.
I write the mileage , both main odometer and trip odometer on every reciept.

With a spread sheet program it is very easy to come up with MPG numbers, cost per mile and about any other thing you want to know.

 

My driving habits have changed a bit in the last few months, and I feel that now is the time to try and get a longer term estimate. The problem was that one upgrade after another came along and I was having way too much fun to get a good MPG average.

I calculate my MPGs on every fill up, but only recently have I been empty enough and conservative enough behind the wheel to see some big improvement in economy. I also run the exact same route every week, so observing the effects of different tuning or driving habits is easier to than if I was all over the place.

 

Here is one for ya. I work with some guys that have picked up "hoopties" to get back and forth from work. They park their trucks and drive them when they need for their farms ect.

They seem to be having a contest to see who can up with the worst one. I think the winner so far is a minivan that the power windows are broke and the windows are stuck in the middle. Baling twine to hold the front bumper on and duct tape on one fender. Doesn't count the other body damage. Runs good though. Had to give $400 for it so you know its a jewel. It is like a 95 model. He said something in the back is making noise now. Loaded 6 or 7 hundred pounds of feed in it and that may have hurt it. Thinks it is exhaust. Saws All with take care of that.