I've been using the Amsoil Series 2000 0w30 engine in 2 cars for about a year now and I believe it's the best oil from everything that I've read on it BUT the stuff is VERY expensive, about $8 per quart when you figure $20 membership needed to order from them (can't buy it in any store) plus S&H for one case, about $85 delivered for a case of 12. I still use OEM oil filters because I'm not convinced that Amsoils oil filters would be any better. So far, I've not left the oil in for even 10K miles. One of my cars has almost gone 7K miles since I changed it (5K the first time) and I'm thinking of having it tested soon as they do that. I'm a guy who use to be very anal about oil changed and rarely go much past 2K using good petroleum oil so it bothers me thinking about older, higher mileage oil left in the engine for 10K miles and scares me to think about going further than that.

Now, I do pamper my cars and I don't skimp on anything for them (don't go the cheap route) but as for price, I'm still not sure Amsoils prices are justified when I think that Mobil 1 is a good product and a 5 qt container can be purchased at Walmart for $17 (less than 1/2 the cost of Amsoil). I'm not presently putting on alot of miles on my cars anymore so I don't need to change synthetic oil very often either, thus maybe the Amsoil isn't breaking me.

I'm planning to switch my trans over to synthetic ATF soon too.

You can read about specs, etc from their website www.amsoil.com but some will think that their tests, etc might be biased too. If anyone knows of any independant research comparing Mobil 1 to Amsoil, I'd also like to see it.