Warm the engine driving or in the driveway?

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Originally Posted by BYprodriver

I agree. The reason they say that is to minimize emissions by warming the catalytic converters as fast as possible, after all Porsche has to warranty emissions parts for 8 years. Also vehicles get very low MPG while motionless.

Yep, also idling the car while stone cold tends to load up the cats with rich mixture carbon. Then the car runs lousy and the cats fail prematurely. Just get in and drive.