I used Castrol GTX 20W50 in the Camaro I had and the Dart when I first got it. After I got the new engine I switched to SAE 30 GTX. The Lucas is just an oil stabilizer that helps the oil lubricate more, and its only like 9.99 at CSK. Right now its on sale at least here in Cali for 6.97, and we sell out of it almost every week wether its on sale or not. Their fuel cleaner also sells just as fast, and a lot of people swear by this stuff. I have yet to use it though.
