Is Pennzoil the best OTC conventional motor oil? It seems to me that people at this web site had basically decided that Pennzoil, Castrol GTX, and Chevron Supreme are the best three conventional motor oils. But some negative information has come up concerning Chevron Supreme (it did not do well in a freezer test) and Castrol. So does this put Pennzoil in a class by itself? In a freezer test the Pennzoil did well and it protects about as good as any other motor oil.