Anybody using synthetic in their four stroke?

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rbstern

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It's about time for an oil change in my Merc 90 four stroke. Wondering if anybody has experience running synthetic in a four stroke outboard and recommends it. If you do run synthetic, do you change the oil less frequently?
 
Synthetics make sense in a gear box or in subfreezing conditions. For every other application a regular dino motor oil is better. With my Merc the recommended weight for a marine oil is 25W40 which you will not find in a synthetic. Marine engine motor oil need additives for best performance and the formulations in terms of the additives is different for outboards than for PWC or a car with its catalytic converter.

The oil should be changed every 3 years even if you only put 50 hours on the engine and this applies to any motor oil including synthetics. With my Mercedes coupe the manufacturer recommends changing every 12 months regardless of mileage so I switched over to dino for it as I put less than 6k miles a year on that car.
 

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