Hello everyone.

Ive been getting really bad gas mileage. I have a 20 gallon fuel tank and ive only been able to get 265 miles average out of it. Most of the miles are highwayand the other is a little local driving. The truck is almost at 104,000 miles, i think 103,8xx. I think its in need of a tune up and i have a leaky header but im not sure if that plays a roll or not. I did the math and it came out that i only get an average of 13.25 mpg. Any ideas would be greatly aprreciated. Thanks.

Phil

 

My 3.9 in my 1995 didn't get the best mpg either, I had a 22 gallon tank and I was really lucky to get 320 miles out of it which translates to roughly 16mpg. I have heard of some other 3.9 owners claiming they are getting 25mpg. I know on my truck it had, had a tune up but the catalytic converter, and muffler were almost completely rotted through so I figure maybe my exhaust was at least part of the reason my mileage was hurting. Get a tune up, make sure you have the right tire pressure, make sure your alignment isn't off replace your leaky header and I bet your mpgs go up.

 

Phil, how many miles did you drive and how many gallons did you put in? Miles per tank is not a good measure because everyone fills up at different times. For instance, I only get about 230 miles, but I fill up at 1/4 tank, so I'm really only using about 15 gallons, which isn't all that bad for the 5.2L V-8 (15-16 MPG).

 

ill fill up from empty and put around 20 gallons and ill get around 400 miles to a tank in my 4.7L and im pushing 20" rims thats about 22 on the highway and 15-17 in town depending on my driving condition

 

What kind of tires do you have? I used to have the mud terrain pattern and it dropped my mpg 3-4. Also you have to remember it is a v-8 and a 4x4 at that. so you have more weight to pull. maybe a good tune up and fixing that leaking header would bring you up. tune-ups are more important than most people think. good luck.

 

I think it's probably a combiation of things that may be leading to your bad fuel milage. Tires play a big role in fuel economy- make sure that they are inflated to correct pressure and that the alignment is good. Stay on top of regular preventative maintenance as well- plugs, air filter, oil, throttle body, etc... These things all add up to effect fuel economy too. It has been said that just replacing a clogged or dirty air filter can improve your fuel economy by up to 10%. Use cruise control when possible, and do your best to keep your speed below 60 mph or so. Alot of research has been done to find the optimum fuel to speed ratio, and on most vehicles the sweet spot is around 60 or so. Anythingfaster thanthis, and your fuel economy drops dramatically.

And fix your exhaust leaks too.

 

i'd say tire pressure would get you a couple..i remember the other day when we were drivin around it looked like your tires were low and the one front one was especially low. i'd check that out and get them all around 40 psi or so.

 

o2 sensor, especially pre cat.

 

if you dont put the same amount of gas in each fillup the numbers will never be the same...some pumps shut off at different times when filling. id go to the same station for fillups to get a better read on actual MPG's.

i think the easiest ways to increase mileage is a tonneau, a clean air filter, keep the A/C off as much as possible,and tires. as far as tires go, check them at least once a month for pressure and if you have a 4x4, id put on more of a street/mileage tire if you dont do any heavy offroading. heavy mud tires hurt mileage...i think you can get a good mileage tire that still looks "truck-ish" if you know what i mean.

 

Thanks everyone for the replies,

MY tires do need some air cause they are low. Ha. When i fill up from a quarter tank, around 17 gallons goes in. I actually might be getting more miles to a tank han im thinking cqause i dont think i ever factored those extra gallons and miles in. Ha. I beelieve the truck is in need of a major tune up which i should do to it. Thanks again everyone. After i do a the things you guys suggested, i'll give an update.

Phil