27 mpg is good on the highway, however 30 mpg average is easily obtainable, of course driving habits are the biggest factor in your MPG. I average 30 mpg at around 70-75 mpg, the only modification I have is a front Plog and a ported rear manifold, stainless magnaflow resonator and K & N drop in filter (stock air box), 2000 GTP. I keep my front tires around 34 psi, and 30 psi in the rear. Most of all a steady and smooth foot on the accelerator plays the biggest part for obtaining best MPG.