What is the current recommendation on synthetic engine oil?

[Rich Stidger]

I have a 1998 Volvo Penta MD22L and the owners and service manuals say to use Diesel oil rated at CC or CD. This is an old spec so what I use now is CF, which is commonly available.
The oil specification from the owner's manual is shown in the table below:

Since I use this engine in the northeast summers I use SAE30W weight oil. It may be Rotella, or any other brand-name manufacturer.

Here is my question: What is the current thinking on the use of synthetic oil? I use full synthetic in my cars and small engines and I still maintain a 4-5K mileage change with filter in the cars and a 100 hour or yearly change in my small engines.
But I am wondering if I should change to full synthetic in my Volvo marine diesel? If yes, what would be the rationale and benefit?

 

[Rick D]

Here is my question:

What is the current thinking on the use of synthetic oil? I use full synthetic in my cars and small engines and I still maintain a 4-5K mileage change with filter in the cars and a 100 hour or yearly change in my small engines.
But I am wondering if I should change to full synthetic in my Volvo marine diesel? If yes, what would be the rationale and benefit?

I'll be interested in the answer. Since I do my Yanmar yearly, and since it is well within the recommended cycle, I feel fine sticking with non-synthetic. However, I do use it on my Ford Edge and 01 Jaguar, but not the 94 Miata and 74 Jaguar. Just concerned about those engines and low annual mileage before changes. On a side note, I had the cam tensioners replaced on the 01 Jag and the mechanic was so impressed he showed me the one they pulled out of the car in the next bay and compared it to mine and told me the PO must have been using synthetic. Good luck on your decision; you are braver than I.

 

[Mark Maulden]

Here's some reading material
Coxengineering.sharepoint.com
Sorry, dont know how to link on an ipad. I've been using Delo 100 since i rebuilt my MD17C a few yrs ago. Now the 30w is discontinued. My last change was with Delo 400 which has a rating of CF-2 and it smokes a bit. In 160 hrs, it used about 1/4 qt which is a little more than with the 100. I would not go to the synthetics for older engines...

 

[Benny17441]

Rich, as much as I have read about the benefits of synthetic oils and listended to other people's experiences and testimonies I have to admit I have not seen concrete proof that synthetic oils provide any benefits over the use of regular oils. Wether to use synthetic oils or not has become a matter of what claims you may believe or not. But you may decide to get some insurance and follow the idea of "I do not know but just in case let me use it". But then are you sure it won't cause any harm?

 

[Charles Erwin]

I am with Mark and Cox on this.

In addition, why synthetic when you are changing at 100 hours anyway?

The central point - in study after study - synthetic offers no advantages when oil changes are frequent and that is the case for 98% of boats because few see more than 100 hrs between changes.

Chas

 

[hewebb]

I use Mobil 1 for Diesel and change it at 25 hours. Universal engine is normally run weekly, however, on small lake not for very long at a time.

 

[Justin_NSA]

I am with Mark and Cox on this.

In addition, why synthetic when you are changing at 100 hours anyway?

The central point - in study after study - synthetic offers no advantages when oil changes are frequent and that is the case for 98% of boats because few see more than 100 hrs between changes.

Chas

That's a good argument. I probably put less than 5hrs on my Yanmar per season but I change it every year. Unless there is much better startup protection, I see no advantage to synthetic for many of us. I use Rotella. They also have a synthetic and they market it under better fuel economy.

 

[Benny17441]

I have one instance where I believe synthetic oils have a true benefit and that is in transmission lubricants. A transmission is a clean and sealed environment not subjected to high temperatures nor significant contaminants. With the way we use our boats synthetic transmission fluid would not require a change for decades. That is a benefit. I have not now changed my transmission oil in about 10 years and do not intend on doing it any time soon. Check the level periodically and so far no leaks. Perhaps regular transmission oil would perform just as good but the added price of synthetic for a single time change was no deterrent.

 

[Justin_NSA]

I have one instance where I believe synthetic oils have a true benefit and that is in transmission lubricants. A transmission is a clean and sealed environment not subjected to high temperatures nor significant contaminants. With the way we use our boats synthetic transmission fluid would not require a change for decades. That is a benefit. I have not now changed my transmission oil in about 10 years and do not intend on doing it any time soon. Check the level periodically and so far no leaks. Perhaps regular transmission oil would perform just as good but the added price of synthetic for a single time change was no deterrent.

I agree with this. I plan to change mine over to synthetic. I've done it to my cars.

 

[Stu Jackson]

Rich,

dino

hasn't changed any over the years

do a search on synthetic on this or any other boating forum, you'll get the same answer

I tried synth once - never again. only time I ever saw ANY evidence of leaking around my oil pan. YUCK.

It simply isn't worth it for older engines.

 

[Benny17441]

Stu has a point, there have been some reports of oil leaks when SO used in older engines and transmissions but I have not experienced the problem first hand.

 

[Mark Maulden]

I know of several instances when people changed their cars over after using conventional oil and ended up with leaks (years ago). Usually around fwd/rear main seals. If that happens on the boat, and it didn't resolve itself even after changing back, it's an engine removal to fix or put up with it. Not worth it IMHO...

 

[Rich Stidger]

I know of several instances when people changed their cars over after using conventional oil and ended up with leaks (years ago). Usually around fwd/rear main seals. If that happens on the boat, and it didn't resolve itself even after changing back, it's an engine removal to fix or put up with it. Not worth it IMHO...

Hmmmm. A year or so ago I changed from conventional to synthetic oil in my 2007 Hyundai. A month ago when changing spark plugs for the first time at 141K I found oil in the spark plug well for 2 out of 6 cylinders. The fix required pulling the rocker covers and replacing the rubber seals at the bottom of the wells. Now I am wondering if I caused this leak by switching to synthetic oil.

 

[SEMPERAVANTI41]

My boat has a Yanmar with a turbo. At an additional $10.00 or less per change for synthetic I think it a small price to pay for the superior resistance to heat, particularly needed for the turbo.

 

[dziedzicmj]

It simply isn't worth it for older engines

If you use synthetic from the beginning (when the engine was new), you probably had less wear, especially during the cold start time. However, I have seen situations where the synthetic oil caused substantial leaks (internal and external). This is, mainly, because it can dissolve and wash old deposits that sealed your old engine for years or affected the seals and gaskets. The problem is that switching back to the "normal" non-synthetic oil would not help in that situation.

If i understand correctly, the main advantage of synthetic oils is that they perform the same regardless of the temperature and provide protection at higher temperatures. In a car, especially, in cold winters, this is an added benefit (when you start the car at -30 (doesn't matter if F or C), you want the engine protected right from the beginning). I imagine that the great majority of sailors do not experience engine starting at these temperatures. The high end might be an issue if your engine overheats. But it shouldn't.

Marek

 

[Benny17441]

My boat has a Yanmar with a turbo. At an additional $10.00 or less per change for synthetic I think it a small price to pay for the superior resistance to heat, particularly needed for the turbo.

The superior resistance to heat of synthetic oil has been documented. It does not improve lubrication but does extend the useful life of the oil. The difference of whether it is beneficial or worth the extra cost still rests in the number of hours at which you change your oil. Where I find that SO provides greater instant protection is when an engine overheats as regular oil can degrade significantly more than synthetic. I have made it a practice to change oil (any) right after any overheating incident.

 

[Rich Stidger]

Thanks for all the comments and ideas. I think I will stick with conventional oil. And I think I will go back to conventional oil in my older cars as well. I did not know that SO can cause leaks. Being old school, I knew that switching to detergent oil from non-detergent is detrimental, but I had no such knowledge about SO.

 

[vhoisington]

I used Mobile 1 in my Yanmar 2gm20, no leaks, no problems. I have been using SO in my cars for years without any leaks or issues. In my trucks and SUV's (2004 Chevy 2500, 2012 BMW X3, 2016 GMC Canyon) it has been working for years. The Chevy has 212k miles, runs like new with no leaks, the BMW uses SO from the factory and I switched the Canyon over on the 1st oil change. I tend to do a lot of over the road driving (denver to San Francisco, to phoenix, etc.) and have no issues.

For my boat, I switched as soon as I got her, Since we sail on cold lakes to start the season it seems to work better on start up. however the 10 minutes its is run each week doesn't tell much about the value of SO over regular oil.

Probably more a matter of preference and choice, good luck.

 

[odaydokay]

The rule of thumb that goes way back to the 1970's is: Do not use a synthetic in older engines that were delivered new with conventional oil. There is no upside and can be large downsides like seals leaking etc. The other rule is if the engine/vehicle was factory filled with a synthetic, do not use anything except synthetic and preferable the original type including weight.

 

[Justin_NSA]

This will not resolve. For every opinion not to use synthetic there is an opposite one for doing it. Run what you want to. None of them will damage your engine.