mobile V-twin in mine.

Anybody know if running non merc oil would create any problems with engine warrantys ? I only have stock small blocks.

I've researched this. Merc's website states to use their oil. Then is says, if none available, then using a good grade oil is ok. However, I've heard that marine oil has additives that deter water ingestion.

They actually have additives that encapsulate the water molecule and keeps them in suspension the the oil.

Ken

Correct me if I am wrong here guys..and I am sure someone will!lol....but I believe the only reason you would not want to run synthetic is either...you just built an engine and you are better off on break-in with a mineral based oil.....or.. with synthetic oils sometimes the roller lifters tend to skid rather then roll because of the lubricity (too slick) of the synthetic oil..but Mobile 1 has been said to not have this problem. I run Mobile 1 20/50 in my HP500 and I can see better oil pressure with it over the syntec blend 20/50

If the roller is sliding/skidding on the oil film how can it wear out? Piston rings ride on a flim of oil and can go hundreds of hours. Pesky Varmint Still saw the honeing marks on the cylinder walls. This is not uncommon with a quality oil.

Ken

Well, I see where you are going with that..but in fact what happens is the roller will get a flat spot if it is skiding more than rolling and eventually end up wearing down a cam lobe.

The other reason to not use synthetic oil in a Merc 525efi is if it's still under Merc's warranty! They say no, no, no to synthetic. I got this info from the brass.

If you are worried about warranty, use a certified oil based on merc's specs. That is currently NMMA FC-W.

I'd probably go with Amsoil Marine Synthetic.

http://www.nmma.org/certification/pr...asp?y=FC-W2007

Out of warranty, Mobil 1 15-50.

Let me clear up my comments: I am refereing to Mercury Racing, not Mercruiser or Mercury Outboards. I was informed by Mercury Racing brass, that they do not authorize synthetic (Amsoil, Mobil 1, etc.) to be used in the "blue" motors while under warranty. I disagree with their stance. I have heard more than my share of arguments for mineral oil and for synthetic oil. I'll leave it at that.