So my problem is my 2002 5.4 Supercrew getting 9mpgs with combined highway/slight around town driving on a good day. I've searched forums, checked my truck and i am just stumped. August of 2010 my truck was turn apart motor wise and replaced cleaned from the block up. New head gaskets, heads got resufaced and cleaned, New injectors, new timing chains and tentioners, throttle body cleaned. New spark plugs. At the time the truck was running 34" BFGs and stock 373s. Then i would get around 10-11mpgs i think and this was the milage i was getting before the motor work. Before i drove my truck back to Tx I added 4:89s to the rear and 38"s. I think my average Highway milage from NC was 12-13mps. And i was completly horrified. I was expecting at the least 15 highway. I drive the truck as light as i can because i know the milage sucks and still cant raise it. The engine responds well, I step on the throttle and it picks up and gos. I have a friend with a stock 02 and I compared highway rpms.
His were
50mph - 1400rpm
55mph - 1500rpm
60mph - 1600rpms

Mine are
50mph - 1550rpm
55mph - 1700rpm
60mph - 1850rpm
65mph - 2000rpms

So they arent too off I dont think. As far as performance engine is stock with the air filter hood cut one of those free mods, dual exhaust from the manifolds back. So I welcome any and all reasonable suggestions. Especially guys running 38s and 488s. Thanks

 

That might be normal MPG's for how big your tires are and how much lift you have on your truck. You didn't say how many miles are on your truck and if they replaced the front O2's when you went through you motor. Worn out O2 sensors can effect fuel mileage.

 

Only way your gonna fix that is buy a Honda for a DD and keep the truck for fun.

 

Well Ive seen other trucks with the similar setups and getting better milage. I have about 155K on it, but like i said last year it got new chains and stuff. I am going to change out the O2s ive known they have been over due for awhile. I think lifespan on them is like what 80k? That is next on my list.

 

LOL. I have a 06 Explorer for DD that I get about 18C/24H Mpgs so no Honda for me. Im just concerned about the MPGs on my real truck.