Chevy and GMC Duramax Diesel Forum banner
1 - 1 of 11 Posts

· Premium Member
10,627 Posts
The rim size has nothing to do with it, it's the overall tire size. 34" tires will kill your mileage every time, no doubt.

The bullydog tuner is definitely not the best for duramaxes. It has pretty sloppy tuning, there's lots of room for improvement.

If it's all about mileage, not about looks, I'd put the lift down as low as it can go, get some smaller tires, or get some better gears. That combined with a different tuner should get the mileage up some.

another option is to try running in 5th gear in manual mode. That will get the rpms up a little so the engine isn't lugging and sucking down fuel.

Let me know if I can help!

1 - 1 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.