Originally Posted by jginnane

Car bought new; just broke 20K. Currently 27.3 miles per gallon; 90% highway driving (average speed 72 mph).

The car has had two recent changes:

(1) at 19K I put on Continental "ExtremeContact DWS" all-season tires in a +1 size on base 18" rims, 35psi front and back.

(2) At the last oil change, went from Mobil One 5w-30 (synthetic, normal grade for Z) to 0w-30. (K&N filter, of course).

The trip computer's been reporting in the 28mpg range on the highway, and the 27.3 is averaged with all driving over two tanks of premium unleaded, or about 500 miles.

The tires seemed to be less than a 5% increase -- barely noticeable. The oil change improved my gas mileage from 23.5-24.3 to the present figure, about a 10% increase.

I'm amazed at this number and wonder if I'm catching nothing but tailwinds the last couple weeks. This is way outside the bell curve, and I don't drive like it's a Prius.