flatlinerz, I've often asked the same question. Its so hard to beat $27 for a five-quart jug of Castrol Edge Extended Performance, Mobil 1 Extended Peformance, Pennzoil Ultra, Mobil 1 0W-40 Euro, all oils that have teams of highly paid scientists and racing experience, with all the latest and toughest spec approvals. I'm not saying Amsoil Signature is bad, indeed all indications are that its comparable, just expensive.