I have a 1999 dodge ram 2500 cummins short bed with a 5 speed manual 4x4 with 89000 miles on it and was wondering how i could get better mpg? Is there any chips, intakes, exhausts, synthetic oils or other tricks to get the truck a couple more mpgs? Im getting about 18 now and would like to try to get it up to 20.

 

I would start with synthetic oil all the way around. Then look at your tires, rolling resistance is a big chunk. Brakes dragging? Change your driving habits maybe even changing your routs. Some programmers claim to improve fuel mileage, but the tendency to play defeats an gain.

 

I average 20 mpg, but that includes alot of hauling: http://www.fuelly.com/car/dodge/ram_...eguides/259273
The highest I have got is 27.7mpg (calculated by pump, not computer). Cruise control at 55 for 70 miles of freeway. Stock size tires, 4.10 gears (not ideal for freeway), and a completely opened up air/exhaust way (cold air intake, intake manifold, heater grid delete, turbo-back straight pipe; 4" down pipe to 5" all the way back). I do have 2wd, but I think you can get into the 20's with 4wd. What rear axle ratio do you have?
Not sure about this but might be worth looking into:
http://www.dieselpowerproducts.com/p...e-cummins.aspx

 

would increasing my tire size from 265 to 285 make enough of a difference to see a visible increase in mpg?

 

More weight and rolling resistance, so probably not.

 

http://forums.4wdmechanix.com/topic/...el-efficiency/

 

on my 98 12v I run 265s Mishilen Ltx load range E and run them at 70 front and 60 psi rear on 2007 alum rims and I run 285 bfg ats load range E on my stock steel rims at 40 psi due to rim being too narrow and causing ballooning / center tire wear , There is no comparison between the 2 for power and millage , I swap them out quite regularly when towing my travel trailer , the narrow tire with mild thread pattern on the CORRECT width rim for that tire and aired up near max is the way to go , I may try 255/85/16 toyo m55s next on my stock steel rims

 

An Edge EZ and a set of Bosch RV275 injectors would gain you approx. 2.5 - 3mpg