Im don't usually bother getting involved in the best MPG threads. But, your aveo must be a 2009? and a manual? I only say that because the 2009 had a tighter gear ratio than the 2010-2011. Its marginal, but i think it was about a 300 rpm drop at 60mph?. They changed the ratio for the US emission mpg requirement change.

I *think* it might have changed twice, again between 2010 and 2011. But I am not entirely sure what the ratios became each time. It might have been @ 300 rpm after both transitions.