dstad

How do you get the best mileage out of a first gen.
I have a 91d250 non i/c, 3.00 rearend, full 4inch from turbo back, 3kgsk, timing at 16.5, couple turns on fuel screw, custom fuel pin and bahaf. I know driving with a light foot, and less than 5psi of boost helps, but is there anything else??

The_Head

Park it and don't drive it.



Thank you, thank you, I'll be here all week.

Cummins says keeping EGT under 700* and boost under 10 psi is best for fuel mileage. It was in an old issue of the TDR my brother had form a few years back.

wannadiesel

Set the AFC as tight as you can stand it. Smoke = wasted fuel.

dstad

Tight??? So tighten the spring

wannadiesel

Yes, run the star wheel up until you find the truck is too doggy off the line. Also back the smoke screw out.

JustRamIt91

make sure your tires are balanced and wheels are aligned. A fresh coat of wax, nicely polished, with rain-x on the window. You may see 1-2 mpg increase. I think there is an adjustment you can do to the trans if its an auto... if its manual idk. Something else i've noticed a pick up on... fresh oil in the rears, synthesis works well but sometimes leaks right back out. i stick with the dinosaur oil.

Trebor

Non aggressive properly inflated tires roll a lot easier than the big oversized aggressive ones. Running the engine much over 2000 RPM's also makes your fuel mileage drop.

Boatnik

A tighter torque converter will help and shedding a few pounds will too. The truck not you. . Drive like you have a raw egg under your right foot and you don't want to break it. Stay below 55mph.

sdubfid

Run alcoa aluminum wheels, 235/85/16 tires with lots of pressure. Swap in a ford 9" rearend to shave a couple hundred pounds. Put on a small spoiler below the front bumper about 4" tall. Close any gaps on the front end with tape. Aerodynamics play a big difference. Cut holes in the rear bumper to allow air to escape.

The biggest difference will be how you drive. Using the brakes is wasting energy.

440trk

Aluminum wheels and skinny tires will help.

No, no, no and no.

A ford 9" takes just as much HP to turn as a Dana 60/70. Not to mention its a weaker differential.

The front spoiler isn't going to increase aerodynamics of these trucks by any worthwhile amount. The added weight and VERY limited effect would most likely hurt more than help. Lowering the truck may help, as it will reduce the initial air deflection by a small amount. Bottom line is these trucks are bricks. They are NOT aerodynamic. Live with it.

Holes in the rear bumper will do NO good.

Aerodynamics doesn't really come into effect on a vehicle until approximately 60mph or so anyhow, so if you want to save fuel, keep it under 60mph. A tonneau cover can help as it streamlines the air flow over the bed a little.



True!

440trk

While a good idea to keep the vehicle clean, it makes absolutely NO difference in fuel mileage.

Firstgenfanatic

I remember reading in some science publication: For every 300lbs dropped, fuel mileage increases 1mpg.

sdubfid

The 9" would be for weight savings. If they can be made to hold up to a 1000hp drag cummins they will hold up for a 1st gen. On a 3rd gen I bet you could shave 3-400lbs by going to a built 9inch. On a first gen maybe 200-300lbs.

A 4" lip on the bottom of the front bumper would weigh maybe 2 lbs and would make a difference at highway speeds. A full belly pan would be best. If it can make a difference on a tdi or civic it would make a difference on a truck. Not huge but everything adds up. Same with the rear bumper. Its like dragging a small parachute if you think about it. You add .2mpg here .5mpg there and they all add up. Yes these trucks are aerodynamic as a brick but doesn't mean there aren't improvements to be made.

Camshaft plays a large role in mileage for the engine. Friction coating bearings, thermal coatings on pistons and head ports to keep heat in the chamber.

In the end it all comes down to money. 9 times out of 10 you are better off just living with what you have and driving with an egg under your foot

JQmile

Get a gear vendors and drive 55 mph.

With my 727 I've gotten:

19 mpg 70-75mph
23 mpg 60-65mph
27 mpg 50-55 mph

Aired up tires help, so does a grille block and electric fans (about 3 mpg gain) if you don't tow and can live feeling like your truck is overheating all the time. (note-when I did it, it never actually did overheat, but it ran a lot warmer)

440trk

HUGE difference between a built 9" and a stock Dana, but its still a silly suggestion. It still takes more HP to turn a Ford 9" than it does a Dana 60/70. So you're already sacrificing some MPG right there. You're going to spend THOUSANDS of dollars for a properly built 9"...and while it can hold up to drag racing (btw, drag gears are softer material than street gears for a reason), the reality is, a 9" CAN NOT hold the weight for hauling and towing anywhere near what a Dana 60/70 full floating rear is capable of. There is a reason most 3/4 and 1 ton trucks use a full floating rear.


In theory...maybe. In reality, no. Adding frontal area to a truck that is already has such a crappy CD is not going to help much. Adding a Belly pan just isn't realistic for a street truck. You would be MUCH better off lowering the entire truck to limit the clearance and the associated turbulance created. THEN the front air dam might start to be effective. Belly pans work great on vehicle that are low to the ground (same with front spoilers)...but a stock height full size truck just sits too high to take advantage of them.

You're comparing Apples and Oranges. Besides, even a TDI or Civic (which are MUCH lower to the ground) still aren't low ENOUGH to fully take advantage of belly pans.


In theory what you are saying is true. However in real life application, specifically a truck, the effects are non-existant. Most folks would think removing the tailgate would improve aerodynamics, but that has been proven false over and over again. There is approx. a 1" boundary layer of stagnant air over the entire surface of the vehicle when cruising around 60mph or so. Anything that is within that 1" or so boundary, has little effect on the aerodynamics. Did you ever notice how you can stick your hand straight out the window at 60mph, you feel a pretty significant wind resistance...but if you put your hand within the first 1" of the body, there is little to no resistance? The airflow over and around the rear bumper is a turbulant area, due to the airflow both above and below the truck. Putting holes in the rear bumper in reality won't due much, if anything (besides weaken the bumper)


All true...also fairly expensive and not realistic unless you are competely rebuilding the entire truck.

The suggestions you offered are not cost effective.

I was looking into the possibility of a GearVendors OD for my truck...but at $3k, it would take me 10 years of driving to start saving any money. (truck is not my daily driver) Fuel would have to get over $5 a gallon again to make it even remotely cost effective.