Engine/Transmission (1998.5 - 2002) crapy fuel milage need help figuring why

[Mhannink]

ok so heres the deal after 3 different turbos 3 different injection pumps and 4 different sets of injectors my fuel milage has not changed a bit. now before you think wow thats a lot of doe for parts to change the fuel milage its not all from me i happen to know the history of the truck. as it happens to be bully dog 8s mach 5s jammer 5s and stock injectors he fuel milage never changed. has had a stock a hotrod and a h. o. pump on it again mileage never changed. has had a stock turbo a bell usb 62mm and a silverbullet 62 on it and again there has been no difference in milage. truck runs good and feels good and strong but it will not get above 16 mpg empty at 65. whats wrong im getting tired of fueling so often.

 

[GCULP]

my only guess would be trying to turn that big of a tire with those tall gears. Also, if you adjust how far the truck is actually traveling with the oversize tires from stock, assuming you haven't re-calibrated the odometer, you're getting betting mileage than you think, especially with all that fuel and air you're supplying to it.

 

[Mhannink]

well yes that is a valid theroy but why but one the speedo is recailbrated and seems to be pretty acurate. also why can other trucks run this same size tire and get 18 and 19 mpg. ive got a buddie that has a 97 and gets 23mpg at 70-75 all highway with simalar tires and gears. though his is a stick

 

[CNeubauer]

Have you checked your AIT sensor? They seem to be a common cause for low fuel economy and they aren't that expensive to replace.

 

[John - K5AWO]

I would bet that if you had someone else drive the truck that is known to be conservative, it just might get better mileage.

I just made a 400 mile trip at 62 mph w/cruise all the way and 99. 9% interstate from start to finish. Never shut it down, 3 minute breaks every two hours. Held the rpm at 1950 regardless of being OD or not on hills. Pulled a car hauler trailer with a Goldwing motorcycle on it.

That trip netted about 20-22 gallons of fuel burned. A previous trip with my son driving the truck empty and running 85 mph burned 35 gallons of fuel.

MPG is a sticky wicket. Too hard to control all the parameters, especially between different trucks unless they are identical in setup.

 

[Mhannink]

well i drive rather conservitive. 2k rpm shifts and as little smoke as possible. run 70 to 75. i did a trip to monteray about 200 to 225 miles never went above 65 cruise all the way with only about 10 miles or so in the city. i got 15mpg for the whole trip. the truck has had 4 different owners and several other drivers truck to the best of my knowledge got over 16mpg. so as far as im concerned the driver variable is not an affect.

 

[CanadianCarGuy]

I got 19mpg once with my dinky tires tires that came with the truck, now I average 14 to 16mpg with 22" rims with 14" wide tires. They are the biggest tire I could fit in the wheel well.

 

[MAllen1]

I have a 99 5-speed 4x4 shrt bed and 285/75 16s. After I recalibrated the speedometer I went from15. 5-16 up to almost 18. Two months after that I put that flexalite fan on the truck it jumped up to 18 in the city/ 20 on the freeway ( 1 m. p. g gain----I know, but u can tell the difference in the power).

 

[WardJ]

18 city in my commute. 20-21 highway if I don't have my foot in it all the time. 10. 5-11 towing the rig. I don't baby it but I don't pin the throttle at every opportunity. All hand calculated.

 

[Mhannink]

yeah see i drive like you guys ill blow smoke now and then but yet i cant break 400 mi on a tank

 

[georgej]

Clessie Cummins once drove across the US and found if he kept the EGT's at 600* he got the best mileage! If you have gauges,try it.

 

[JRBurton]

My 2001 has stock size tires, FASS 150 and 4" exhaust system . HO , 6 speed , amsoil all around , 354's in the rear. Drive 70 MPH & stand on it at least once a day and am getting 21 MPG highway and city. Towing w/my 8000# TT at speeds of 70 and get 15 MPG.

 

[DPrew]

For having an auto trans and over sized tires those numbers don't sound bad. I get about 18 mpg with my six speed if I don't hot rod.

 

[2-ND TIME]

fuel milage!

Well for fuel milages I do envy you gents my gutless wonder :{. I get 24. 2 now with the fedex pump and the 300 injectors, that is down from the 25. ?? for the imperial gal. Most of my Liters for 100 km is in the 9. 9 to 10. 1 range. But very little power I hate being passed by vans. There is a capacitor somewhere that is bad in mine. So yours (capacitor ) is in good condition this is the reason that you have power if you are able to check the voltages with a good multi- meter or an oscilloscope that will tell the truth of things.



By chance does your engine sound tinny when you give it throttle I bet it doesn't.

 

[Mhannink]

with a fully built auto i would expect better. then 14 to 15 average

 

[bdoody]

I have a 2001 auto, edge ez, Dr Performance injectors, 5" exhaist and I can only get 16mpg empty. It embarrasses me that all you guys can get close to 20. Not sure what is wrong in my case as well.