Well EWF that's exactly why Amsoil cost so much more than Mobil 1, simply because it is way better. That's why they require to flush the motor before hand because they don't suggest mixing the 2 together. Mobil 1 is a great oil for the dollar but Amsoil is the leader being the originator of Synthetics, they know a thing or two about making superb lubrication and they prove it.
