I�m getting 16-18 out of my 05 suburban Z71 with a 5.3 gasser

I'm getting 19 average with my 2010 6.7L Cummins. 23 mpg at 70 MPH.

But, I plan on swapping in an LBZ duramax and Allison 1000 (6speed) combo, NP263HD transfer case, and the rest of the 3/4 ton running gear with a Dana 60 straight axle steer axle under my suburban. That should net me a 3-5 more MPG gain.

I have a little seat time with a 6.7l 4x4 crew. Never saw those numbers.

Averaged 15 on a good tank in my 2010 suburban 4x4. Not talking hwy mpgs.

Little disappointed towing with the f250. The Ecoboost is just hard to beat. It digs deep and lugs things out. The 6.2l is quick to downshift and spends WAY too much time in 3rd at 4k rpms. It does tow straight. Feels solid and the brakes are first rate. Just feels underpowered for a 10k trailer

I just got to my destination after towing a heavy trailer down I45 with my F250 Superduty diesel (6.7 bypassed and tuned). I couldn�t maintain my usual high speed required on 45 but I did manage to cruise at 80 and it did it well. My average mpg dropped from 17.5 to 17.3.

Towing heavy, 80 mph, 17mpg.....sure.

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Hey! I�m just telling you what it said. It�s a long term average. I still burned the whole way on a single tank.

Just caught you didn't reset.

Did you get the 3.73 gears? That is a common complaint with them, most I talk to say if your going to tow with it you want the 4:30'S.

I would be ok with it grabbing for gears, at least its trying to get to an rpm it can do what your asking of it at. My biggest complaint with my last few GM gas trucks was they just didn't want to downshift, always tried lugging itself till it just couldn't.

Yes, 3.73. I'm still learning a few things. If I lock out 5th, it's a lot less likely to drop to 3rd. Otherwise it seems to bypass 4th. And towing in 4th or 5th isn't too bad but 3rd.... the engine is friggen loud!

Averaged around 7 mpgs over 360 miles. Not much different economy. Love love love having brakes.

I always hated that with my GM 5.3 if you gave it a lot of pedal it would drop straight from 6th to 3rd, nice if your were wanting all it had, but an annoyance most of the time.