Amsoil is the best at one thing: Marketing. They have to be. They make some stellar products, but they also make some mediocre products too. I've used them off and on in several vehicles. They are high in perceived value but I question what the ROI is. When you factor in an annual PC membership plus shipping costs, their products price themselves out of the market. Especially given how good the last 2 API categories have gotten, it's getting harder and harder to justify their benefits.