Synthetic oil in a 4 stroke?

[muskiechaser]

So here's a question I hope some of you more experienced 4-stroke owners can answer. I recently bought a 75 HP Merc 4-stroke and I was wondering what your opinions are on sticking with the Merc oil or going with a synthetic like Amsoil. I have been running synthetic oil in all my vehicles for about 15 years with no problems. Just wondering what everyone else does.

Thanks, John

[jltimm]

I run Amsoil in my 99 Yamaha 50 hp fourstroke. I change it every year, although it probably doesn't need it. Pretty cheap oil change. Just a couple qts. of oil, and a oil filter.

[theoilman]

AMSOIL recommends not going longer than annually. Condensation, rust protection, etc.

AMSOIL now has the NMMA certified 4-stroke marine lubes, available in 10W-30 (prod. code WCT) and 10W-40 (prod. code WCF).