I own a new 05 Subaru Legact GT. Today I made the switch to GC 0W-30 at 3200 miles. First off the car idles like a completely different car. Great improvement. Car used to idle like crap, now it's hard to tell if it's running. Second, mpg went up significantly. Was averaging 20.5mpg and now after 150 miles on CG I'm at 26.8mpg. Can't tell if there is any performance increase. BTW - It was the Gold GC for what it's worth. Figured I'd spread the good word. Also, just got off the phone with my wife who's 04 Subaru Outback with 20k miles has been running and idling like crap. She made the GC switch too this morning and had a 200 mile business trip. She says the car is unbelievable. Running and idling like a luxury car. I'm impressed. She was previously running Mobil1 5W-30 EP. I am a total skeptic. I don't believe in snake oil. Can't stand Mobil1. I've used it in several cars with no real noticable difference. But this GC stuff works. Don't know or care why, but it really works. Thanks to you guys at BITOG for all the hard work to my benefit.