I have Chevron Supreme 5W-30 in my 1999 Silverado 6.0L right now. Over the past serveral mornings it has started very well at +10 to 11 degrees. There may be a SLIGHT drag initially, but I attribute that to the original equipment 1999 battery in the truck, and the fact that the headlights come on as soon as the key is turned to "start". No piston slap and good quiet running overall. At first startup, the engine is quiet enough to hear the idler pully/belt tensioner bearing squeel a little. Only problem in 60,000 miles! First nice day it's getting some grease!
