I just installed one less than a week ago and haven't seen any difference. In fact I'm seeing less efficiency.

In hindsight I should have bought the "disposable" Fram I pick up at the WalMart and replace about every two months. In fact, I'll probably go back to the Fram to see if there's any noticeable difference.

Meanwhile, I'm relatively new to the car, but I've become obsessed. Hence I'm taking baby steps and trying to make inexpensive "performance" upgrades.

In a bimmer forum expense is all relative, but I can say an inexpensive "performance" upgrade is an oxymoron

-B