- Oct 12, 2017
I have a 91 Fourwinns with an OMC Cobra 5.8L (ford 351 (Cleveland?) block. Going to change the oil in the next couple weeks and wondering if anyone recommends adding STP oil additive or simmilar Zinc additive. I'm set on straight SAE 30 oil - either meijer house brand ($2.39/qt), QS (3.49/qt), or valvoline ($4.39/qt). Probably going to go with the meijer house brand due to lowest price for 6qts. I've searched around some of the boating forums but cant seem to find a straight or trustworthy answer. If anyone has any experience with or knowledge of ford 351 based OMC's please feel free to chime in. Thanks! If nothing else, would it hurt anything?