[project1971]

I have a 98 tahoe with a 5.7L get 17 pretty consistent. I had the intake gaskets changed at 77k (when i bought it)has 108k know just to put better ones on it and got rid of the junk orange coolent (causing the gasket failure) and flushed it several times and refilled with green coolent. My 95 c1500 extcab 5.7L get 13 city driving. don't know on highway and has 216k miles.