been having poor milage since i got the truck 3years back it had 175k now has 230k had it to oregon diesel to have it checked 200+$$$ later the tell me everything was ok!!! and that some trucks just dont get as good milage!!! what next the truck is stock except k/n air filter and 4"strait pipe! they here me coming hahah! i thought i would change the o2 sensor next what u think

 

My 99 has never got good milage. My 90 did far better.
I think its the nature of the beast.
Welcome to the site fellow Coastal Web Foot.

 

mine doesnt do all that good either 13-15 thats about it.

 

im talking bad average 9-10 the best was 12 unloaded going to try larger tires and have the speedo recalibrated! change to o2 sensor !i like the truck but hate the milage everybody i talk too gets way more!! maby thats whe the previouse owner sold it!!!!

 

Too bad you did not have the truck since it was new. Did the truck always have bad mileage? If so I would look at injectors before the O2 sensor. No codes? Check the fuel pressure.

 

what is your truck? is it a diesel? if so i think diesels do not have o2 sensors

 

yes it has allways got these milage#s 98 1/2 ram 2500 4x4 diesel 24v was reading some treads here and was mentioned about the o2 sensor!the injection shop said injectors were fine! im stumped!

 

What is the gearing on your truck?? 4.10 rear end??? It sounds like that may be the case. If so, you can probably do some tire mods to get your mileage up. I have 4.10 rear end and bumped my mileage by 2mpg just by putting on larger tires. The stock size for my truck was 245/75R16 and I'm now running LT315/75R16 (35 inch) tires. It's about a 4 inch increase in tire size from stock but it brought my gearing down to about 3.61 or so, so I'm running pretty close to where a stock Cummins would run as far as speed and mileage. Let us know what your gearing is.

 

the glove box says 354 on the gearing! has anybody tried that turbo thing that u put in the intake tube???? to increase milage. i bought a lift kit and some 37'' hummer tires and wheels see if that helps miliage will install in june

 

try cleaning your intake air temp and map sensors. it could also be a week VP (not able to advance the timing )

 

My '99 3500 dually gets ~15 around town, and a best of 20.5 on the highway.

Alot has to do with the way I drive, agressive starts and passing everything on the road will kill my milage by 4-5 mpg.

 

thanks guys will try your ideas was going to replace all the sensors because of the high miles!!! again anybody tried that super charger thing that goes in the intake tobe??????? are they worth it if not ille spend the money on something else!!thanks mel

 

Im sittin close to 230k miles, on a 99 4x4 5spd w/ the 3.5 gears and just tossed on a edge comp and been romping and bat outta hellin every stoplight.. and still get 17mpg combined about half city half driving on that tank.. 285/75/16 tires. Mileage did go DOWN from the old 235/85/16's, nearly a year ago.

Something definetly is wrong with your truck to get that low of milage.

Whats your fuel pressure at?

Check all your connections for leaks?

Did you fill up at the same pump? Have you tried different stations?

Sometimes some stations ive noticed will kick off ealrier than others, some have higher foaming fuel, etc. So a "fillup" at one may leave the tank with as much as 2 gallons less than a fillup at another station.

 

muffler plugged?

 

....any of those "Turbo-Intake" super-Mechanical snake oil gimmicks are a complete waste (referring to the items you mentioned that go into the intake tube: Think Blockage and Restriction!)

There are a lot of places to look, clean the sensors (I've never heard of an O2 sensor on a diesel?!?), and post your gauge readings, maybe they will point us all in the right direction.....

DO you have the auto or manual? Have you cleaned the fuel filter (screen) and swapped out the fuel filter?