RPM, thats why i use Diesel rated oils lol. I think im gonna stick with rotilla for summer and the 0w40 petrocanada for winter. worked great for me. and yes, tool box will be coming out. gonna go over the whole truck clean clean clean it and get some of that paint on bed liner stuff. might also do the out side of the bed sides. they seem to collect so much dust it isnt funny. Also the rear fenders, the front half of the left side takes a licking from rocks on the gravel roads!