I have never gotten better than 28 MPG highway since day 1, 2011 LTZ RS. I've brought it in more than once while it was under warranty. I waited about 10K miles figuring the engine needed to break in but it never got better. Dealer blamed it being the LTZ with 18" wheels causing more rolling resistance. I can believe that affecting MPG to a small extent, but not a 20% loss in MPG over a slightly slimmer tire. I was getting better MPG in my C6, and that has some very wide tires.
I'll be trying some Tehran. Having other issues right now though.
I'll be trying some Tehran. Having other issues right now though.
