I have the Lucas additive because it was the best additive I could find locally (Canada). I read up extensively on the additives and found the Lucas had the "proper" zinc formula. It comes in a 16 oz. bottle, but you only need to add enough to bring your engine oil zinc level up to par. You'll need to find out how much zinc your current engine oil contains and add the Lucas accordingly. If you research engine oil zinc content their are several independent studies, buy the best oil you can and top up the zinc. I did all this 8 months ago and can't remember the exact numbers. The readily available good oils contain about 1200 ppms of zinc, if you add about 1.5 oz. of Lucas it will bring it up to the "recomended" 1800-2000 ppms. The Lucas bottle has the content on the side, you'll just have to do the math.