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Synthetic oil for a M-35B

robbjd

.
Nov 17, 2020
4
Catalina 34Mk II 1344 Sarnia
Does anyone use synthetic oil in their Universals? Big sale on oil this week and I'm thinking of switching to synthetic. Engine has 1800 hours on it.
John Robb
"Mystic"
97, 34MkII
Hull #1344
 
Jul 1, 2010
861
Seaward 25, Catalina 350 Erie, Pa
Personally, I wouldn't bother switching unless the motor called for synthetic (M35b doesn't). I've always been happy with Rotella T4 in all my diesel engines. If I did switch, I'd go to Rotella T6 (synthetic) or the Delo equivalent. I do use synthetic in my car engines, but am rethinking whether that's even worth it.
 
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Likes: JamesG161
Nov 6, 2006
9,202
Hunter 34 Mandeville Louisiana
If ya do, it needs to be real diesel oil not gasoline engine oil.. If the oil and filter are changed every season, there is no real benefit for going to synthetic over a conventional premium diesel oil like Rotella T4.. or its Mobil/Chevron/etc equivalents
Your boat, your choice. .
 
Feb 26, 2004
21,893
Catalina 34 224 Maple Bay, BC, Canada
If ya do, it needs to be real diesel oil not gasoline engine oil.. If the oil and filter are changed every season, there is no real benefit for going to synthetic over a conventional premium diesel oil like Rotella T4.. or its Mobil/Chevron/etc equivalents
Your boat, your choice. .
Well, since I am the "Your boat, your choice" guy, I wouldn't and I haven't. I've read enough bad press about synthetics eating seals so I made the decision to NOT make the change. I have a 1986 M25 engine.
 
May 24, 2004
6,765
CC 30 South Florida
If you are going to change the oil and filter seasonally then you might as well use a premium refined petroleum oil. As the diesel engines age the oil will start turning black sooner and sooner. The small particles that turn the oil black are just not being picked up by the filter and are not particularly harmful. Oil is about viscosity and the principal enemy of viscosity is heat or dilution. If the engine suffers an overheating condition then it is prudent to replace the oil as soon as possible. Synthetic oils are more resistant to heat breakdown but are equally susceptible to contamination and dilution. It is true that there have been a good number of complaints from people with older engines that say they developed engine oil leaks after switching to synthetic oil. If you want to run synthetic oils in your transmission this is where they shine with long longevity and a sealed clean environment. But to me paying the price of synthetics to use seasonally in the engine is not worth it and is not worth it either to run the risk of leaks on older engines.
 
Feb 14, 2014
5,619
Hunter 430 Waveland, MS
I've got to wonder where the carbon goes in the synthetic oil
Synthetics are chemically made from Methane, thus avoiding the distillation of crude oil.

The bottoms off the crude oil distillation columns were a crud and a plague.
We now use that crud to make Asphalt.

Your boat, your choice..
Jim...
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
Lousy choice of words on my part.

The petroleum lubricating crankcase oil starts out its life a clear light amber colour. After a couple of engine operating hours, it's blacker than midnight. This is the result of the particulate carbon from the products of combustion entering the oil.

You've said that:
My synthetic oil never turns Black.
If the synthetic oil is not picking up the particulate carbon from the products of combustion, where does it go ?

BTW ....................................
Your boat, your choice..
methinks that borders on plagiarism.
 
Feb 14, 2014
5,619
Hunter 430 Waveland, MS
If the synthetic oil is not picking up the particulate carbon from the products of combustion, where does it go ?
Out with the exhaust or in the oil filter.

We looked at the oil and filter again, although not any engine hours this year.

Still no need to change the engine oil.;)

In a good year of sailing, we might have maximum engine 300 hours.
______
methinks that borders on plagiarism.
OK.... My boat, screw you guys....:cowbell:
_____
I've read enough bad press about synthetics eating seals
Still wondering where they are on my Volvo Penta.:huh:
____
We dont have any seals in the Gulf of Mexico.:cowbell:
______
If the oil and filter are changed every season, there is no real benefit for going to synthetic over a conventional premium diesel oil like Rotella T4
Or your might want to read this propaganda... [Even a video for you Claude:biggrin:]
Shell Rotella® T6 15W-40 Full Synthetic

Jim...
 
Last edited:
Jan 19, 2010
938
Catalina 34 Casco Bay
Whether or not you make the switch, your old selection must be diesel rated. That means a "C" rating..i.e. SAE 10-30 CF... Do't be fooled by HD... Diesels oils are CE, CF-4, CG-4, CH-4, CI-4, CH-4, CJ-4 ( not the Jeep ), CK-4.
Each progressive letter after the "C" indicated a step forward in oil technology..
 
Jun 11, 2015
2
Catalina C-36 Mark II Winthrop Harbor
Does anyone use synthetic oil in their Universals? Big sale on oil this week and I'm thinking of switching to synthetic. Engine has 1800 hours on it.
John Robb
"Mystic"
97, 34MkII
Hull #1344
I switched to Mobile 1 years ago. Engine runs smoother and quieter. I have a M35AC
 
Jan 4, 2006
3,820
Hunter 310 West Vancouver, B.C.
OK.... My boat, screw you guys....:cowbell:
A mite harsh, but well stated :clap:.

Out with the exhaust or in the oil filter.
Referring to the lack of carbon in the synthetic crankcase oil ........... that can't be true as petroleum lube oil continues to get blacker by the mile . The carbon is NOT being picked up in the filter and continues to accumulate in the oil.

My synthetic oil never turns Black.
Why doesn't it accumulate in your synthetic oil ?

"Enquiring minds want to know" as once quoted by that investigative quarterly, "National Enquirer" :cool:.

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Mar 20, 2016
491
Beneteau 351 WYC Whitby
Unless you have rebuilt your engine with Viton seals like they switched to in automotive stay away from synthetic Buna-n does not like it. And as far as transmissions its too slippery and will cause clutches to slip. I have a hurth transmission which uses dextron 2 or 3 non synthetic . Do you know how many people dump in semi or full dex 3 and then say the transmission failed and is a piece of junk
Stick with what your manual says
 

Attachments

Jun 11, 2015
2
Catalina C-36 Mark II Winthrop Harbor
I have used synthetic for over 10 years and have not had one of these problems. engine runs smooth and trans shifts smooth.
 
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Likes: JamesG161