today a friend of mine came to me and is looking for ways to increase the milage on his 97 ext cab 4x4 cummins. what would all you guys say is the top 5 things he can do to his truck to get better milage. hes seeing about 200 to half a tank so 400 to a tank. the truck is bone stock by the way. i had some ideas myself but i wanted to see what you guys have to say.

 

Narrow non-aggressive tire inflated to high pressure.
Driving like there is an egg between your foot and the accelerator pedal.
Keep the rpms under 2000.

 

Having the 3:55 gears instead of the 4:10s .
Synthetic lubes for everything .
That makes 5 [ with Bills ] .

 

What about replacing the fuel filter? It might be dirty!

That makes at least 5 1/2.

 

besides these things what else hepls like exhaust, intake? i was thinking of turning up the star wheel to get him that extra umph off the line to get that thing going a little faster.

 

The biggest problem is the wind resistance. To get better highway mileage, simply slow down. There is one.

If mileage is the goal, check all of the brakes and bearings to make sure that they move freely and make sure the tires are properly inflated.

If you are going to mod the engine, an intake and exhaust will help a tiny bit and bumping the timing will help a little. Adjusting the star wheel will not help.

Put the truck on a diet. Since F=ma, the less weight you have to accelerate, the less fuel you burn.

If you want to go really crazy, try lowering the truck or building a taller air dam.