With a GMT900 Tahoe, I've typically obtained highway mileage of ~18MPG at 75-80 MPH. That's a truck with more power, more weight, and more frontal area - and the same transmission.

The Atlas is a neat engine on paper, but in reality, it serves as justification for GM's OHV V8 strategy.

 

It hasn't had much done to it in the last few of years. 10 years ago, premium V8 engines had 275-300 HP and V6s were considered powerful if they had 220. Time marches on. I imagine that it's very expensive to engineer the same sorts of changes to multiple lines of engines.

If GM add DI, dual VVT, and all the other enhancements in the uplevel 3.6, the 4.2 (actually maybe it would be 4.4 or 4.5 if it got the same enhancements made to the other Atlas engines) would probably be 330hp and better economy to boot. But how would GM justify spending the $$ on those changes to an engine that fits only in larger trucks, and how would it position that engine against the V8?

 

Are the small trucks set to die in a couple of years?

 

Bingo. The HF V6 can fit in both cars and trucks; the Atlas isn't nearly as versatile. GM can no longer afford to create ump-teen different engine lines, as it's increasingly expensive to keep an engine up-to-date, and GM isn't exactly rolling in extra cash.

I'd much rather see GM investing in smaller clean diesels (like the new 4.5L) and alternative fuel technologies than spending money on an engine that's limited to one or two platforms.