If you really want to protect your motors for long life and possible resale value, look into Amsoils fully synthetic oil and gear lubes. Lower units especially will benefit from there gear oils. You can join for a small ($10) fee. This entitles you to better pricing than say Napa Auto or other retail suppliers. Just order from a local direct distributor and pick it up from them to save the shipping costs. A very cool deal. I have been running it in my 2'stroke 130 Yamaha and 4-stroke Yamaha 8hp-High thrust kicker. My 1996 Tacoma 4 wheel has 195,000 on Amsoil and runs as good or better than the day I bought it. Trans, front and rear diffs have a service change interval of 500,000 miles!!!!! basically life of vehicle. Engine oil change intervals of 5000-7500 miles for 5-30 SAE.or twice a year if you're smart. Google Amsoil to find local direct jobbers, No i'm not ,just a big fan. Just like it when my Chit works the way it was meant to.