T6 is 5-40 synthetic, not 15-40. What I use, buy it in 55 gallon drums from my jobber.Thanks for all the input. Amazon's price for a gallon is $44 including freight. However, I will be buying my oil from Walmart. I will probably buy Rotella T6 15W40 synthetic oil.
One thing I do that most people don't do or aren't aware of is, I send a sample to Blackstone Labs every change and have them do s spectroscopic analysis. That way I can track whats going on inside my engines as well as depletion of additive packages. I do that with every engine I have except the lawnmower and tiller engines. Good insurance against impending issues.