marine engine oil

[turf1]

A straight synthetic 30 weight is Amsoil ASE 10w-30/30. I have used it for years in golf course equipement with good results.

 

[JimPghPA]

I have been learning a lot about oils from BITOG and a few other sites. Somebody please correct me if I am wrong, but from what I have read this is the understanding of what is going on.

There are two ways to get multiple viscosity oils.

Your standard low cost dino 10W-30 that is used in many cars starts off with a 10 weight oil and adds viscosity improvers. Those improvers can shear under demanding use and if they do the oil looses some of the upper number viscosity. Your engine manual is trying to steer you away from using this kind of oil. This is why they do not want you to use a non-synthetic, and do want you to use a mono-grade synthetic.

The other way to get a multi grade is to start with a very good synthetic base stock. A good example of this would be GC. It is actually a straight weight 30 oil made from a very good synthetic base stock. There are NO viscosity improvers used. The 0W-30 rating is because the natural low temperature behavior of this base stock is that of a 0W.

Like wise many of the higher viscosity oils, are made with a very good synthetic base stock, and have NO or very little viscosity improvers. If you read the Mobil 1 web site about M1 V twin 20W-50 you will see that it is a very shear resistant oil, and that it also has additives to prevent moisture from causing problems.

From what I have read, GC would be a very good choice for your engine as it is a straight 30 weight synthetic, even though it is specked as 0W-30. What is most important is that the oil be a full synthetic, and NO or very little amount of viscosity improvers making the oil shear resistant.

Also with the re-writing of the rules by M1 a few years ago about what is called a full synthetic, it is a little harder to know what group(s) the base stock came from.

Full synthetics that are JASO-MA rated like Rotella T6 5W-40 would be shear resistant, and a good choice. It would also be low in cost, you can get it at Wal-Mart in gallon or quart containers.

M1 TDT (Turbo Diesel Truck 5W-40), and Delvac 1300 would be other good choices. Also,Redline, and Scheffers make some outstanding great base stock oils. You could give them a call.

The last I heard Rotella 10W-30 is not JASO-MA rated and therefore would not be a good choice.

 

[lars11]

Don't use 5w or 0w oils in marine engines. You won't need the low temp properties and they are also potential problem oils in marine situations. Whatever oil you choose, make sure it is a high viscosity oil like 15w40, 20w50 and the likes. Amsoil straight 30 may be a good choice and have a 10w rating too. That, however, does not make other 10w30 oils suitable! Beware.
If you have 4s outboards, pick the recommended oil, my recs are for io and inboard gas and diesels.

 

[Pete591]

I like 20W-50 Mobil-1 V-Twin in big-block offshore performance boats.

 

[Bror Jace]

For an off-shore racer (or any other serious racing application) I would prefer a straight weight. After all, you are looking at a handful of 'cold' starts (max) and after that, 98% of the time the engine is at operating temp.