I've been hypermiling for over a year with my SE-R, and it needed to pass a smog check this year. I was worried that P&G might keep the catalytic converter too cool to handle emissions, or (worse) might contaminate the cat. So before I took my car in for the smog test, I took if for a 20 mile drive to warm it up. Force of habit, and my never-ending quest for FE had me P&G my way to the halfway point. Then I drove it back on the freeway at 55 mph to light the cat for 10 miles. Unfortunately, I got to the smog check station, and another car was in the bay being smog checked. My car and its cat sat cooling for the next 15 minutes. To make a long story short, my car passed with normal results.