Well I just got a GSR (used to have an LS), and it has about 30k miles on the engine rebuild. I'm a delivery driver and I've been considering switching over to Redline Synthetic motor oil or Amsoil motor oil. My question is, since I start my car often, maybe 10-15 times a day, which weight oil would be the best? I am thinking of 10w40, 5w30 or even 0w30 (40?) be a better viscosity for start up protection? I don't race OFTEN but it's important to me that the oil I choose can hold up when I push to 8000 rpms.