Regular vs. Synthetic

Apr 26, 2014
30
Oday 34 Cape coral yacht basin
I have bought a 1984 O'Day 34 with a 1996 Universal 25XPA. The owner I bought it from was using Shell Rotella oil. I am going to change the oil in a couple of weeks and thinking about changing to a synthetic oil. Should I leave well enough alone or go for the synthetic. I have always used Mobil 1 in all our vehicles throughout the years. Thanks for any input
Patriotsway
Frank
 
Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
I think synthetic oils are great as long as there are no wet clutch plates involved such as in motorcycle trannys. That said: I do use synthetic oil in all my automobiles but I do not use all synthetic. My feeling is to get the synthetic benefits but not the extra cost. I use 1 quart of synthetic and the rest Valvoline or Castrol GTX. I studied oils while in college and found it very informative.
Chief
 
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
I have bought a 1984 O'Day 34 with a 1996 Universal 25XPA. The owner I bought it from was using Shell Rotella oil. I am going to change the oil in a couple of weeks and thinking about changing to a synthetic oil. Should I leave well enough alone or go for the synthetic. I have always used Mobil 1 in all our vehicles throughout the years. Thanks for any input
Patriotsway
Frank

Personally I would leave well enough alone...
the only advantage to a synthetic oil is the higher sustained operating temperatures that they can tolerate without breaking down...
Small boat engines normally never get to those high of temperatures unless there is a problem elsewhere..

The Rotella T is a good proven oil and has everything you need in it to keep the engine well lubricated.
 
Feb 26, 2004
23,047
Catalina 34 224 Maple Bay, BC, Canada
Syn has been reported to eat seals. Why chance it? Why spend the extra $$?

Do a search on this forum on synthetic and you'll see.

What seals, you ask? How about your oil pan seal. Creates a yucky mess. For ABSOLUTELY no good reason.
 
Jan 30, 2012
1,142
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
'Yacht auxiliary engines generally run for short periods, at lower temperatures than any other duty, and typically in the lower half of their rev range. From a lubricant point of view this is a very undemanding duty, accounting for their low API requirement. Combustion temperatures never reach levels at which a high-performance lubricant can be effective, so the overall chemistry in this area is not neutral but alkaline (basic). There is a great deal of evidence to show that use of an oil with a TBN that is too high for the duty can lead to several problems, particularly high wear rates of cylinder bores. The effect of high TBN engine oils in accelerating wear rates is well known. Burning high TBN oils may generate excessive deposits on the piston crown. As the piston tilts when moving up and down these deposits become compressed and will form a very hard and abrasive layer, causing excessive wear, mainly in the bore.'

The above according to Cox Engineering. Use the syn in your car - not in the yacht diesel.

Charles
 
Jun 8, 2004
2,955
Catalina 320 Dana Point
Leave well enough alone, Shell Rotella and Chevron Delos have been the preferred oils for diesels for decades.