I am wondering what oil I should run in terms of synthetic weight, I know 5W30 is recommended but if I can only get 5W20 or 5W40 which one should I use?

I have a cupon for buy 4 bottles and get 2 free from valvoline synthetic and I can't seem to find any 5W30 from Kragen's since its on sale for $3.99 a qt there.

 

I use 10w30 mobile 1 synthetic, runs great, walmart has good price on the 5 quart jugs