quicksilver is mercury oil,they did a test on oils in bass and walleye mag a few years back and they said all oils have to meet marine industry standards so one is as good as the other,that excluded dfi oils.my dad and i use pennzoil.his motor sets and it hasn't rusted up,i run the crap out of mine and it hasn't blowed.they told my dad mercury would not honor the warranty and they would take oil samples if there was a problem but they actually can't do that,but if they get you to pay 20 for a gallon of merc oil instead of 11 for a gallon of pennz thaen they come out ahead.you can use any that is tcw3 rated.heck i got a 4.5 i used lawnboy oil in for years and it still has the hone marks in the cylenders.