I use the Starbrite 10W30 Synthetic blend in my customers 4 stroke outboard and the Sierra 18-9680-2 full synthetic gear lube vs the 18-9650-2 synthetic blend due to the the full is used in the Volvo unit. I subcontract service to a customer that has about 35 Volvo units and about 100 Mercruisers in dry-stack along with about 75 outboards and since I switched the unit over to it I have not had any leaking seals or drive failures in 3 years and some unit are 12+years old......
