I have a question for you cummins guys. I have an 04 6.0 f350 I get 13.6 highway. But that's running 75 an 80 mph. Down I75 from Indiana to Florida.about 1000 miles. My question is what speeds are you talking about when you say 20 - 22 mpg on the highway???

 

I noticed better mileage with 35's and a manual. and 33's with the auto. How good of shape is the air filter in changed the fluids?

 

ok so i have a questtion. why do i get 13 mpgs on my 99 no matter how fast i run or if its in or out of town?

 

Change the fuel filter, clean your injectors, get a lift pump. The more fuel restriction, the harder the pump and motor have to work... the less fuel mileage your getting. With a clean burning, no restriction motor you will get good gas mileage. Unles your running stright -10an lines than that a whole lot of non-restriction

 

most of the highways where i am from are posted 65mph so thats what i consider highway of i went on the interstate at 75 it goes down to 16mpg. just the simple fact of the more rpm's the more fuel getting burnt

 

remember driving habits. and the faster you go the more resistance. my 01HO with 4.10 gears, edge, and 4" exaust gets 21mpg at 60 and 17mpg at 75. i always say if you wear brakes out every 30k you will get bad mpg.