Here in AL the temps regularly see 100+, and i run 10w30 Castrol Edge.

 

10w-30 amsoil is all that i use in my engine..

 

try 20w-50 next erl change !

 

same here but i started using the 5w40 rotella synthetic. i figure if its good for big rigs with turbos then it should be good for me. this is the smoothest running oil i've used so far. i used to run nothing but mobil or RP but it would always pour out like water when i would change the oil. it seemed to break down alot more than the rotella.

 

I'd go with a synthetic 5-40. Rotella is good. You can also get it in Castrol and Pennzoil. Maybe some other brands but those are the ones I know for sure.