I'm just throwing this out to all of you for your thoughts/comments. I had 5 quarts of GC that I'd been saving for a project car that has now been delayed for quite a while. I finally couldn't wait, so I used it for an oil change in my 1994 Ford T-Bird with a 4.6 V8 (112,000 miles). I haven't had any trouble starting the engine, and the temp around here has been ranging from 40 to 75 degrees since I did the change about a week and a half ago. However, I've noticed that the car seems a bit more sluggish and not quite as quick in the acceleration department (especially when I'm trying to accelerate while at 40-50 mph). I'm worried that this oil could be too thick for my particular engine's service requirements, but wondered if there was anyone out there that could give me any advice, especially if you have experience with this engine. I don't want to put a strain on my oil pump or start losing performance, especially since my car is 15 years old and I need it for a lot of short-trip city driving to and from work. Any comments/advice would be appreciated. I'm trying my best to be objective and not just imagine these "symptoms" in my car. Thanks.