I run 1/2 bottle of STP (blue bottle) in the oil in my plow truck (350 SBC), I run Mobil 1 synthetic in it.
I would run a full bottle, but the oil thickens too much in the cold with that much STP (6 quarts).
Been together now for 2 years (after the last cam went south) so I'm not sure how good that is (as it hasn't been that long).
