Now that I can't seem to find Valvoline SAE 30 weight Racing Oil, I'm not sure what to switch to. I prefer a single viscosity since I live in a hot climate with 114 F as maybe the extreme surface temp. Winter temps can run as low as 28 F. I'm running a 3 y.o.(just off warranty) 350 GM crate motor thru a SM 465 4-speed. Feedback?