Gas Guzzling / Different Wheel Size w/ Gas Mileage ?

["Mike Theuri" <mikesoft@conwaycorp.net>]

I have an 88 80Q with about 160K+ (odometer is broken).
Previously I had an '86 325e Bimmer. In comparison I'm
finding my car a gas guzzler. I don't have its exact gas 
mileage but I had presumed that I would get atleast 30mpg
but I keep finding myself having to dig deeper into my 
pockets for gas money than I previously did. I got a set of
tires for the front, they are 195/65. The one's at the rear 
are 195/60. Remembering that the Q is all wheel drive, 
would the slightly different sizes for the front and rear 
have any negative effect be it gas mileage or any other
problem ? If anyone has the approx.. gas mileage please
let me know so that I can monitor mine. I usually shift up
to 5th as soon as I can so as to economize on gas. If
there's anything I need to check to reduce my gas 
mileage, let me know. Thanks.

Mike Theuri
88 80 Quattro