I got a set of 33 in tires on my 2001 5.9 6 speed 3:55's with a banks boss tuner straight pipe K&N performance air kit. I have noticed my mileage isnt as good anymore on the digital display. Its average is 16 to 16.7 when it used to get 18 to sometime 20or 21 on highway. Is it because my tires are bigger than stock and are throwing off the average mileage indictor? Thank for any input. I was also wondering if I put som Jammer stage 3 on if it would hurt my mileage.

 

Lara you need to hand calculate you mileage to see where it really is. The computer can be effected by tires size and different mods. You should fill in your signature so we know exactly what you are working with.....

 

There are two things going on. If you haven't corrected your speedometer, the truck things it is going slower and less far than it actually is. This will result in lower fuel mileage readings(even hand calculated if your odometer isn't corrected). The other thing is that your bigger tires will hurt your in town mileage since they have much greater rotational inertia. Depending on a few other factors, they may even help your highway mileage but they will definitely hurt your mileage in stop and go driving.

 

since You are talking about mileage, how much should I get with a 95 ctd, 5spd tranny and 4.10 behind? regular tire size for a drw. oh the engine has mods for about 300+ hp.

Thank You.

 

I would say 15-16 all day long in the city and 18-19 on the hwy if you keep the rpm down

 

It depends completely on your driving style. If you keep it at 50mph, you could get over 20 but realistically, it is tough to drive that way most places. High rpms are not good but lugging is just as bad. Since you have a 4.10, you will be running higher rpms than optimal on the highway. The big killer on these trucks is windage. If you were to drive at 65mph, I would suspect that you should get 18-19mpg on the highway and 15-16 in town.

 

That is not so bad, I get the same mileage right now with the engine I have but half the power . I guess a GV or USgear is the way to go for highway driving then.

Thank You.

 

i was the one getting 25 on average with my 97 so i would say that that mileage is possible. but that was with stock 215inj and a little hx.

 

I get about 17 on the highway doing 60 to 65. I have 285/75-16s and 4.10s. I'm about to put a fuel pressure gauge on to see if my lift pump is shot. If that is not the problem I know my timing has slipped. If so I'm going to bump it to 16. Not too long and I won't care about mileage as I'll be running a WVO system on the truck. Sorry for the rambling.

 

Thanks I will try to find someone who can reset my computer for the proper tire size.