Synthetic Oil in Diesel Engines?

[MrBruce]

I have a Universal Diesel Engine 5411 in my Catalina 27. I changed the Oil to Full Synthetic Mobil 1 5-30 weight and the engine seems to run very smooth compared to regular 30 weight it had in it also less smokey diesel smell. I've ask fellow dock boat owners and a few said they would not chance it in there engines. I like to here what everyones take on this?

 

[Stu Jackson]

There have been anecdotal reports that synthetic oil eats seals. I used it once, seemed the oil pan gasket started to become questionable. Not wanting to do all that work, I went back to dino. It's less expensive, too. M25 engine, pretty much like yours. It's not like we're saving the planet or anything, either, ever notice the tons of dino oil in auto stores?

 

[Marc Robic]

Being in the automotive industry for the last 20 years, I can tell you they synthetic oil technology has greatly improved. For example, concerning seal and gaskets, today's quality synthetic oil have additives that will actually help improve seals and gasket performance. But because synthetic oil is thinner, if a gasket is somewhat already in poor condition, it MAY leak. The good news is, as stated before, many higher quality synthetic oils offer additives that will help older gaskets swell and restore any prior minor leaks.

What is good to know, is that the medium and long term benefits of synthetic oil is the reduced wear and tear on engine components, easier starts, better engine preservation during those long winter months (for us Canadian sailor..).

However, be careful of the myth that using synthetic oil will prolong the oil change intervals. Although. Synthetic oil will not break down as fast as regular oil, the oil change intervals recommended by the engiene manufacturer must be respected.

Lastly, for those that may not be aware, if you want the full benefits of synthetic oil, make sure you also use a synthetic oil filter!