while hanging out in a friends business, auto parts, repairs + engine rebuilding in the 70's i stripped down a small block chevy + filled a 16 oz coffee can with SLUDGE! the owner i never seen before came in + asked how it looked? i asked did you run Pennzoil, he answered YES how did you know!!! not knowing how the engine was maintained or not Pennzoil had that reputation in the PAST!!! hopefully better as i use the platinum in several family vehicles today!!