For 10 years on my big block Cuda I have used 10-30 synthetic oil. I'm thinking of going to 5-30 synthetic this winter, because the 5wt will flow quicker to the valve train at startup, where most of the engine wear occurs. What do you guys think. I know that there are folks that say on a performance big block, use 20-50wt dinosaur oil, but I've read articles that say you are wasting horsepower by pumping such thick oil. So, what do you think about 5wt-30?