I'm changing my oil yet again at 23000 miles. I have used Mobil 1 5-30 w/good result , Mobil 1 10-30(start up noise, also found defective K&N oil filter part of problem) , and the current GC 0-30 . Right now I would like to try RL 5-40 or maybe Amsoil. Any feedback greatly appreciated. P.S., I'm still underwarranty.