[jmatta]

stateof...I used to fill with Royal Purple because my Porsche wrench swore by it. I changed over to Castrol Syntec 10W40 due to it's excellent write-ups and value over RP. I would think in Texas, you'd have even better luck running a 50 weight with the heat. I'd also suggest looking into the LN low temp t-stat and a coolant flush; you could lower your coolant temps by 20-25 degrees, which translates into lower oil temps.