Casey,
I have a CK20HST and I have been using the Shell rotella 5W40 syn, year around since first oil change. Changing at 100 hr intervals now. I buy it at Walmart or TSC, price is about the same, I think it was $22 for 4 qts at TSC last time.
Starts easy in any weather, no sludge or varnish in engine, doesn't burn a drop either.
I live in Rochester, so you know it can be below 0 one day and 40 the next and back again.
I also run 10w40 walmart syn in my Chrysler minivan. I'm a sales rep and drive an average of 35000 a yr. I change the syn every 15,000 and the filters evry 5,000 and add a qt. I have 170,000 on it now it purrs like a kitten, and the inside of the valve cover is whiteglove clean.