OMG, another oil thread, yep. I have been looking for a good oil to replace the 15/50 Amsoil I have been using because according to the oil grade/bearing clearance guide I should be using a 10/40 or 15/40 group oil. Amsoil does not offer this group in a racing/flat tappet oil. They did tell me I could use their 10/30 no problem, but i'm uncomfortable with that. My clearances are .029/.033. I just found this GP-1 that is offered in a 15/40 group. They claim in a 383 small block chevy 5hp gain and cooler temps just by changing oil. Either way looks like a good enough oil. Anyone here ever use this stuff? They have my interests.