Mileage on 5.7 vortec

[dylan5299]

Hello all,
I just got back from driving 600 miles for a little road trip. I figured now would be a good time to see what my mileage is on the highway. I just used DashCommand for it and it tracked it well with graphs and everything. The results were less than desirable though. I was about 8mpg on the HIGHWAY. This is me babying the pedal too. I just got a tune from blackbear because I have headers, 33 inch tires, 4.10 gears and a new cam. I also got a 3 inch body lift. Do all these factors really make my mileage that poor? I'm not worried about doing a tune up or anything as I already have before the tune.

 

[GaryCCR]

What year is your truck? How many miles? What trans? 2 or 4wd? If it was a tbi 4wd truck with 300k I'd say that's not too awful. How's you air filter?

 

[OutlawDrifter]

To compare with a MOSTLY stock 1998 ECSB Z71. The best I ever saw at 68mph was 17.9mpg. That was on stock size rubber, fresh tune up, no headwind, 3.73 gears, L31/4L60E combo, and running the cruise. Best I ever did on the interstate at 78mph was around 15.2mpg. Only mods were a better muffler and tailpipe setup. 200K+ miles on the setup. One of the cleanest, best looking pickups I've ever owned!

33s and body lift aren't doing you any favors. How fast were you running? Expect lower mpg's with winter blend fuel also. Bigger tires and taller height to catch more wind are really going to pull you down, however.

 

[BowtieBrody]

Was the engine broken in properly after the cam swap? I've heard that from multiple guys I've done work with who have built engines, and they've told me that if an engine with a cam swap wasn't broken in properly it would run pretty poorly, don't know how much truth there is to it though.

And when you say tune-up, do you mean just cap/rotor/plugs and wires? Or did you do fresh filters all around and other such things like O2 sensors and cleaning things?