Three weeks ago, I had a four new tires put on my '96 854T - everything was great, no more steering wheel vibration, better handling and quieter ride. However, my gas mileage has now dropped from 23.6 mpg (city/highway mix) to 22 mpg. Has anyone else experienced this?

Tires: Pirelli P6 Four Seasons, P205/50R-16 87H FR B, inflated to 40 psi

If your new tires have a greater circumference than the old ones, you go further per revolution of the wheels and fool your odometer into thinking that you have not gone as far.

What your odometer says reflects how many times your wheels turn, there is always some error.

Put some 13 inch donut spares on all four wheels and you'll get great mileage.

Check your odometer against 10 miles of highway markers and get an idea of its error.

DO NOT reset the trip meter while you are moving, you may break the gears.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 435,000 miles put on 9 bricks

Yes. Several reasons. New tread is taller and flexes more, which is a slight slip when going straight. Tread pattern and compound will make at least 1mpg difference. After about 5K miles, you should be back to normal, unless you got really aggressive tread.

At least you won't have to worry about hydroplaning and sliding off the road on your old US Bald Eagles :)

Klaus
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The 164 has a new home, all I am left with are 2 turbos :)