[LAX5]

I recently swapped out my Continental Premium Contact 6 tires for the Pirelli P-Zero All Seasons. Wheels are the 22" 742M. My average mpg has been noticeably lower since the change. About 2 mpg less. Looking at the specs, the Contis and Pirellis are about the same weight.

Anybody else who made the swap notice a change in their gas mileage?

[doublezero]

Your 2mpg difference is not the tires. A minuscule rotating weight difference on a 5,000 lb vehicle will be unnoticeable. Same for rolling resistance, very small. Not the roughly 8% efficiency loss you're seeing. Probably just driving conditions, poor fuel quality, air density/conditions, a little more throttle or speed thru turns/hills, etc. These things are all highly variable.

[weinerbarn]

Make sure they are inflated correctly. Some places just inflate to a "standard" pressure like 32 regardless of the vehicle and call it good. Did you change your iDrive to reflect the change in tire type? That will be the best way to ensure you're using the correct inflation pressures.