Re: L/U gear oil question
GL-4: Specified for hypoid gear service without shock loading, but still moderate to severe service (high speed/low torque and low speed/high torque). These lubes may be used in manual transmissions and transaxles where EP additives are acceptable and typically contain a different zinc additive combination. This classification is still commonly used, but is also obsolete. It is also a commonly specified for marine outboard and stern drive lower unit gears and bearings where the manufacturer specifies GL-4 rated performance. GL-4 rates lubes are not recommended as a replacement for GL-5 rated lubes. GL-5 rated lubes shows significantly better anti-wear (anti-score) properties than GL-4 rated oils under similar service conditions <br /><br />GL-5: Specified for hypoid gears under shock loading and severe service operating conditions used in cars and trucks. This is the most common and widely used specification today. These lubes have a high level of EP additives .<br /><br />The minor difference in 75W and 80W is in fact insignificant!<br /><br />Use a Synthetic gear lube in your Lower unit, They have an adaquate amount of antifoaming agent in them tha regular automotive gear lubes do not have!! They will also protect your gears better in case some moisture gets into where it doesnt belong!
