Why are you running such a thick oil, are you burning it or what? You live in TN; your oil doesn't need to be that thick unless you have other issues that require you to use a thicker oil!
My guess is he's using one of the high-zinc oils which are usually thicker. But I agree, you want to use the thinnest oil that still gives at least 15 psi oil pressure at hot idle. Might try some 10W-30 or 10W-40.
