Engine oil...fully synthetic any better?

[bbc3]

We just picked up our new SAN and it's already about time to winterize. The PCM manual specifically says there's no advantage to using fully synthetics, yet I've always noticed a difference in my car (using Mobil 1 vs regular oil). Since we want our boat to last, was wondering if anyone has any personal experience using synthetic oils in their PCM engines? Any help is appreciated--

Ride on...

-Brandon

[NautiqueJeff]

I wouldn't do it until the warranty expires. If that's not a concern for you, then at least wait until you have over 50 hours on it. It should be completely broken in by then. I hope you don't plan on increasing the drain intervals. In a marine engine, even with synthetics, that's just not a good idea.

I did use synthetic oil in my '94. Not sure if it made any real difference or not.

[Hollywood]

Theoretically there is a performance difference, Realistically they are the same. I wouldn't sweat using synthetic motor oil, just keep it fresh.

[HudsonSpeeder]

bbc3,

I would stay with what you have always been using. I have been racing Honda Civic's and Preludes for the last 20 years and yes I use synthetic there but I never use it in my transmission. The reason being is that in causes the oil seals to sweat (leak slightly). From my own experience synthetic oil tends to evaporate because it is very thin. I would use what you dealer recommends and maybe a straight 30 grade. I know in the early 80's Mercury V8's were using 30 staright NON detergent. I don't know what they recommend now but 30 still sounds right to me.

My 2 cents.

[SGY]

Synthetic oils--been down that road in my racing days. I always understood the performance gain was from using a lighter weight oil--which was made possible by synthetic oil. The performance gain due to lessor parisitic drage is minimal--5% or so. When racing I used same weight synthetics just to protect my motor in the extreme conditions. I never expected a performance gain--and the dyno never showed such gain when comparing the same weight synthetic oils.

So, I doubt you would feel any difference in the water. Hence, why spend the extra money when you really can't or shouldn't shorten the oil change intervals--especially when you are using a lighter weight oil. The non-synthetics protect as long adequately as long as you change the oil when called for--no worse or better than synthetic. And, it's not like you are racing your boat. I think PCM is correct when they suggest that there is no benefit in using synthetics in boats. Their benefit only comes in longer oil change intervals because their film strength and viscosity doesn't break down like petroleum based oils.

Just my .02 cents.