I've caught the mechanics gunning the shit out of my car during a test drive when I brought it to service at BMW. Turns out that all test drive = pedal to the metal for the mechanics. I usually reset my trip calculator and get a comfortable 20+MPG but after bringing to BMW I get below 15MPG.
This is why I abuse the crap out of the loaner. If they can't show some respect for the owners car then I will disrespect the loaners.
I do know people that do donuts, burnout, neutral drop on their loaner car..
