I was picking up my car from the shop today and because I use Pennzoil, I told him how much a love it because he's such a Valvoline and M1 fan and doesn't like Pennzoil too much..says it causes sludge..LOL But then he corrected himself and said that really, all oil causes sludge when left in too long and said the BEST way to prevent it is to let your car idle for 3 minutes before you drive it. Anyone ever heard this? And does it really work?