switching to synthetic oil

Jan 31, 2012
56
Catalina 30 mkIII Santa Barbara
I have a 1996 Catalina 30 mk III with a universal 25xp. The engine has about 2000 hours on it and I change the oil once a year. I have been using Delo 400LE oil as it is recommended for diesel engines. I would like some expert advise on switching to Mobil 1 or some other synthetic oil. It would be my desire to expand the life of the engine in doing this. What do you think?
Greg
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
What do you think?
Don't bother. And don't do it. There have been reports that synth oil eats seals. It simply isn't worth it, for both the possible (but not guaranteed) seals issue nor the extra cost for synth. Stay with dino oil, it's just fine.

The best way to deal with the issue of engine longevity is to change the oil regularly. Simple.

PS - This is from 1,800 Catalina 34 owners' experiences as well as multiple boating forum discussions on just this same subject.
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Pretty sure there is no evidence to support the idea that synthetic will extend engine life - sailboat or otherwise. I recall a study that concluded (non turbo cases) synthetic was of no benefit unless oil changes were infrequent. Frequent changes (100 hrs is pretty frequent) were and are most effective strategy to maximize motor life.

Apart from the fact synthetic does not help there are risks with synthetic in motors of your vintage - and they are not simply confined to seals failure Stu Jackson mentions. I do not know where the wives tail about synthetic extending older motor life started but no motor manufacturer I know of requires or recommends synthetics for non turbo motors prior to 2005. Even for new motors synthetic use has got far more to do with air quality than motor life.

Please read the following before you become irrevocably convinced that synthetic has magic qualities for sailboat diesel motors

https://coxengineering.sharepoint.com/Pages/Oilforyachtengines.aspx

Charles
 
May 24, 2004
7,129
CC 30 South Florida
Ditto. The problem seems to be reported more in the older boats. Today's oils are much better than when your boat was built so the current dino oil will be just fine. The secret of good oil is viscocity; the oil can be dirty from particles too small to be picked up by the filter but it will be fine as long as viscocity is maintained. The main enemies of viscocity are heat and dilution. If your engine overheats change the oil and if the rings are leaking excessive raw fuel into the crankcase change oil more frequently. I would change it every 100 hours or once a year whichever comes first.
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Don't. Mix of synthetic with real oil can form sludge. You still need to change oil yearly so why would you change? Synthetic is great for autos that were designed for it like benz.
Sometimes we gild the Lilly and make things worse. Save your seals and your money.
 
Mar 30, 2020
7
Catalina 30 MKII Lake Murray, SC
Hello
Synthetic oil does not technically eat seals but the synthetic oil molecule is much smaller than conventional oil. That’s why you hear people say on an older engine that I never had oil seepage or leakage issues until switching to synthetic. I would recommend conventional oil in this case as recommended by the manufacturer. As another point synthetic does have superior lubrication/slip layer properties. If you have an older pull start push mower you may be surprised at the difference in pull effort with synthetic oil.
 
Feb 14, 2014
7,400
Hunter 430 Waveland, MS
I switched to full synthetic for 3 years now and have had 500 hours running it. [50 HP Volvo Penta]
These are my observations, but I am not saying anything about extending my engine life expectancy of 10,000+ hour.

1) No black smoke in exhaust and only a puff of white on starting.
2) Engine oil changed once in 3 seasons
3) No carbon build up in the exhaust riser.
4) Oil is still clear and not blackened.
5) Oil pressure, on warm engine, is constant.
6) Starts faster then my Ford Expedition.

Since a full synthetic is manufactured and not crude oil refined, there is no lower weight distillate to carbonize.
_____
I did my Genset Yanmar 16 HP also and have similar results [added 300 hours to it]
____
Noteworthy:
My Son-in-Law, who had his own boat repair business, is now convinced to use full synthetics.

Jim...
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
Ive used Rotella T in my diesel trucks for years and started using it in the little Westerbeke 1994 18-2 a few years ago. The engine runs smoother, quieter, and seems to be a little less cranky for it. The engine always rattled, and some days sounds a lot like its trying to throw a rod, but its much less so since switching. If the Rotella is killing it, you'd never know it.