I recently got a Jetta Hybrid and noticed that VW says the car requires premium gas (to prevent knocking and eventual valve damage). I have a friend with a late model 5 series BMW which also requires premium and he has used regular gas exclusively and has experienced no knocking or other negative ramifications for the 100,000+ miles he's owned it. Not wanting to spend more than I have to on gas, I've read up on the ramifications of using regular instead of premium and they almost invariably say that with today's computerized fuel systems, requiring premium gas is a thing of the past. Tom & Ray--The Car Guys--agree:http://www.cartalk.com/content/premium-vs-regular . As an experiment I used regular in my last fill-up and noticed no changes whatsoever. Has anyone else out there tried this? What, if anything, have you noticed (other than a fatter wallet)?