I'm really not sure if the synthetic oil has to contribute to the
quietness of the engine.

maybe so.

I've always been leary of using a synthetic, because I don't have new
engines for one. and I've known of people to change to synthetic on
older vehicles with 90+ thousand miles, then complain because the
bearings are hammered out of the engine. I've always copnsidered that
the reason why is because with bearings with high milage already
"broken in" that they have an excess clearence in the tolorances, which
is fine with a 10 and even 5W motor oil, but when you throw in
synthetic, which initially is thinner than ATF, or water, the viscosity
isn't really changed with heat, but there is less oil pressure because
of the tolorances being opened up so the oil pressure drops.

Thats my view.



trainfan1 wrote:
Big gus wrote:
Hi guys thanks for all the advice
posted in the past.

well me and the guys at the maria were discussing oil.

Some use "marine" grade while others do not

Some use Valvoline strait 50 weigh "racing" oil

was wonder what every ones thoughts were?

Thanks
m



For the rather minimal cost, & maximum protection, I use 5W-30 or 10W-30
Mobil 1 synthetic in the inboard. That engine is as clean as a whistle
and extremely quiet - the loudest noise with the exhaust under water is
a tie, with the belts going around the pullies, or the bubbles at the
transom.

Rob