Oil Synthetic or Stock? Marine or not?
 

I run synthetic in my cars and motorcycles, and noticed that the marine oils have a rating for rust.

I run my boat in a fresh water lake. I think condensation on a car engine would just as bad, so not sure why the marine has the extra "standards for rust" and if that is something to consider (Synthetic does not have that rating)

Thanks for the input in advance

All "Marine" means is they can charge you more.

The only difference between synthetic and conventional oil is synthetic will tolerate heat better, and won't break down as quick.

Translation: If you're terrible at changing oil frequently (anal folks say 30-50 hours, book says 100 hours or once a summer) then perhaps it's best to use synthetic becuase it will hold it's viscosity a little longer. If you're good about routine changes before the oil really starts to break down or get very contaminated (depends upon overall engine condition) the oils of today are much better than the oils of say 1985 and you're good to go. Less expensive, equates to more frequent changes (budget-wise). All that aside there's expense and the all important "feel good factor" lots of folks like to have, or be able to say.

well... while that analysis is certainly down home folksy, the truth of the matter is that pure synthetics outperform conventional oils in every single criterea and , short of the initial break in period, every professional i know or have ever worked with swears by them. and not for just severe duty.

my experience with every major brand of conventional oil vs synthetics (once they became available) in every concieveable circumstance proved to me that there is simply no comparison.

if you care about your hardware, you run the synthetics. in a value for cost comparison it is buying 100 dollar bills for a dollar.