Synthetic or Not ?

After weeks reading through Diesel & Oil forums, the oil issue seems more confusing than anchor(s) ing......
Previous owners of our new to us boat with twin Cummins 6BT5.9 Turbo @ 2600 hrs. have used Shell Rotella 15W-40.

Is there any merit to changing to Synthetic ? Brand ? What weight ? What are the experienced & gearheads here using ?

I have some experience with Synthetics in our gas. vehicle fleet but am at a loss & confused when it comes to marine & diesel.

Tx. and I look forward to your experiences either way ... Frank B.

I like synthetics but experience is limited to vehicles. I start using them when new. Currently have a Ford F-150 with 130,000 miles and have never added a quart of oil. This is not as unusual today as it was when I was younger when one might consume almost as much oil as gas.

Not from personal diesel experience but my takeaway from a Nigel Calder class.
1-use an oil that meets all engine manufacturer's recommendations / requirements
2-if a particular oil, which meets the recommendations has been used regularly in an engine he might tend to continue with the same oil due to some variation in additive packages.

Here is a small bit of info from his class handout:

Tier III/IV engines and synthetic oils:
• CI-4 oil is designed for up to 0.5% sulfur; CJ-4 for up to 0.05%
sulfur (500 ppm ULSD; Tier III engines); higher sulfur content
will affect catalytic converters and particulate filters…
• High sulfur fuels need oil with a high Total Base Number
(TBN) & more frequent oil changes; however, high TBN
encourages piston ring fouling & glazing…
• Synthetic oils: improved viscosity, longer lasting, less sludge
but still need to follow engine manufacturer’s
recommendations…
• High detergent properties – may break loose sludge in older
engines and damage the engine…
• Some engine manufacturers double the oil change interval if
you use their oil…

Greetings,
Mr. ES. As you've found out, oil can be a more contentious issue than, gasp, the "A" topic. You are sure to get a LOT of anecdotal information in response to your post so allow me to be the first:...Ooops, second.

MY opinion only. Stick with the Rotella. Cheaper and will do the job given the light to moderate use you will experience. It's worked for thousands for decades so don't try to re-invent the wheel.

In extremely hot or cold conditions, highly stressed racing engines or when an engine sits unused for long periods of time, synthetic oil has its advantages because the boundary layer of oil will not break down as quickly as non synthetic.
In all other applications, especialy low performance diesel engines it is a waste of money, You are much better off changing your oil and filter regularly and using the OEM approved non synthetic oil. This will ensure that unburned diesel that has washed past the rings during warmup and condensation generated when the engine cools after shutdown are removed and not diluting your oil.
Switching to synthetic oil very often results in oil leaks appearing on a previously leak free engine.

I'm in the engine business and stick with Rotella 15-40 on my personal boat. Just not enough advantage to using synthetic.

One good step was to do an oil sample after say 100hrs. I did a sample at 200hrs and report came back saying the oil was still in good shape, so my change interval is now at 300hrs. I do a sample every few changes and they have been consistently good, even 300hrs is proving to be conservative. Depends on the engine, boat use, lots of factors, but the sample should tell.

I use Rotella T6 synthetic in my vw diesel car, it has a dry aka not water cooled turbo, and running hard on the highway and pull off and that turbo is HOT. Would have to idle it for like ten minutes to avoid it baking the oil on shutdown. So synthetic there makes sense. Boat turbos are mostly water cooled and naturally have lots of idling time to cool thiings down before shutdown.

Yup, I'll 2nd, 3rd, 4th that. Stick with Rotella or like oil that meets and follow your engine manufactures recommendations. There is no "Value Added" to switching to synthetic in this application.

In addition to the wise comments above, I should note that the main benefit to synthetic oil is that it doesn't break down with usage so you can go longer between oil changes. But diesels need their oil changed to remove soot and fuel in addition and that requirement is independent of oil type. Stick with the manufacturer's recommended change intervals unless like Ski you sample the oil and know what you are doing.


David

Dinosaur

I asked the same question to a very good friend that owns a trucking fleet with over 150 mixed Euro and American diesels .He remarked that maintenance was a big expencive problem and if he could spend more $$$ to extend the engine life /fuel savings /------- he would .

When asked what oil dose he prefer he said they all work but he prefers use cheaper mineral oil and change more often than use expencive Synthetic oil and try to get longer life .

Also commented that they ALWAYS have the laboratory analyse the oil on every oil change and recorded against each engine as its cheaper to pick up a problem before it happens . And on a comparison test on 2 new American trucks one using Synthetic and the other using mineral at 800000 k both engines were still running well according to the analysed oil and same average fuel usage .

I asked the same question to a very good friend that owns a trucking fleet with over 150 mixed Euro and American diesels .He remarked that maintenance was a big expencive problem and if he could spend more $$$ to extend the engine life /fuel savings /------- he would .

When asked what oil dose he prefer he said they all work but he prefers use cheaper mineral oil and change more often than use expencive Synthetic oil and try to get longer life .

Also commented that they ALWAYS have the laboratory analyse the oil on every oil change and recorded against each engine as its cheaper to pick up a problem before it happens . And on a comparison test on 2 new American trucks one using Synthetic and the other using mineral at 800000 k both engines were still running well according to the analysed oil and same average fuel usage .

Rotella for us also

Frank...
Lots of prior posts & opinions re: engine oils.

Previous thread -Yanmar - Mobil 1 Synthetic My post #30 has several attached oil report files as well as a link to another thread w/100+ posts & MANY opinions.

The problem I've found with almost all oil reports & recommendation is that they are auto / over the road truck related - some gas engine some diesel but few marine related.

The attached file - Best lubricants for yacht engines - is the best / most applicable for our interests as diesel boat owners... I've changed my opinion and preference re: oils after reading this one - I have little interest in trying to convince anyone to change their opinion but rather to offer up what I felt was a good and relevant study... draw your own conclusions.

Don,
Very good and informative link.
It says under "Viscosity";
"It is a fact of life that it takes more energy to pump more viscous oils around the engine. In the drive for improved fuel economy it is now common for lubricant viscosities as low as 5W-30 and even 0W-30 to be specified for car engines. The disadvantage of these low viscosities is that separation of lubricated components is reduced and wear increased. Modern car engines overcome this by hardening crankshafts, making bearings from various aluminium alloys and other means. This is not the case with yacht auxiliary engines, which universally use traditional metallurgy. Oils with viscosities of less than 15W-40 are thus inadvisable."

15 weight oil being 15 weight at room temperatures (or thereabouts) and 15W40 is 15W (approx) at startup but acts (viscosity wise) like 40W oil at 200 degrees. But it's not 40W oil. It's 15W that has been "souped up" to behave like 40W oil at 200 degrees. The viscosity improvers do not improve lubrication. They displace oil that does and therefore that reduces lubrication. Only a small amount though.

Most trawlers are powered by engines that never see temps below 40 degrees or above 100 degrees. My NA boat engine (Mitsu) recommends 30W oil from 23 degrees f to 104 degrees f. I had the boat in Alaska for 7 years and never had a problem starting or operating when cold and see no need for anything but the recommended 30W oil. However on the viscosity chart they do include two grades of MV oil .. 10W-30 and 15W-40. Personally I think they are included because these engines are frequently found on generators that often are exposed to freezing temps.

So I use 30W RPM Delo oil and change often.

RT Firefly said:

Greetings,
Mr. ES. As you've found out, oil can be a more contentious issue than, gasp, the "A" topic. You are sure to get a LOT of anecdotal information in response to your post so allow me to be the first:...Ooops, second.

MY opinion only. Stick with the Rotella. Cheaper and will do the job given the light to moderate use you will experience. It's worked for thousands for decades so don't try to re-invent the wheel.

Click to expand...

I fully agree with your opinion.

Rotella 15/40 in charter boat (Cummins C) and Dodge pickup (Cummins B). 5,000 hours in the boat and 410,000 miles in the pickup. I'm currently running John Deere oil in the trawler, and will continue to do so through the warranty period. Will decide whether or not to change after the warranty is up.

Ted

Wait, what? Is there a general consensus that Rotella is currently the best option?

The consensus is straight viscosity diesel dino oil changed frequently works well.

The TIME limits , months in the engine, are more important to most boaters than hours of operation.

Greetings,
Mr. NM. A consensus on TF????

If there are no problems, stick with whatever the previous owner was using.

RT Firefly said:

Greetings,
Mr. NM. A consensus on TF????

Click to expand...

Ok, my popcorn is ready. Proceed....

I don't think Rotella is best or even better, it is just that my supplier stocks it in many flavors, at a good price, and it is also available everywhere when traveling. And I have not heard any complaints about the quality, and millions of engines use it. That's good enough for me.

Regarding single weight vs multi weight, probably some good arguements for the single for trawler engine use. But considering most engines in heavy service have gone to multivis and the refiners are putting their RandD efforts in that direction, the multivis oils have gotten very good. I choose to take advantage of that improvement in oil tech.

Basically in the industry we see near zero failures related to lubrication failure. Just not something to worry about.

manyboats said:

Don,
Very good and informative link.

So I use 30W RPM Delo oil and change often.
[/FONT]

Click to expand...

Eric...
I couldn't agree more !
I have become a strong believer in using a high quality (Delo, Rotella, ...)single wt dino oil.
My reasoning is exactly in line w/ your comments re: single vs multi Vis...
and
The points made in the article about additive packages used in the newer API rating multi Vis oils (especially Syn) that are pointed at Diesel emissions reg's and pollution control systems on autos & trucks... that don't apply to us and can actually cause problems.

I used to believe that the newer ratings were always backward integrated and superior - the article changed my opinions and it's the only one I've found that deals w/ marine applications.

Bacchus said:

Frank...
Lots of prior posts & opinions re: engine oils.

Previous thread -Yanmar - Mobil 1 Synthetic My post #30 has several attached oil report files as well as a link to another thread w/100+ posts & MANY opinions.

The problem I've found with almost all oil reports & recommendation is that they are auto / over the road truck related - some gas engine some diesel but few marine related.

The attached file - Best lubricants for yacht engines - is the best / most applicable for our interests as diesel boat owners... I've changed my opinion and preference re: oils after reading this one - I have little interest in trying to convince anyone to change their opinion but rather to offer up what I felt was a good and relevant study... draw your own conclusions.

Click to expand...

Thanks for the file and direction to # 30.

And thanks to ALL for engaging in this convoluted topic .. All your shared experiences are much appreciated .... F.B.

I definitely would't do what the previous owner did ... unless you do your research and find that he was indeed using an oil that is 100% suitable for the engine. The previous owner may not have known enough to choose the right oil. Another exception is when the PO was using what the engine manual recommends. Most all the time you can't go wrong w the engine manual.

However it is often said that one should stick w a brand over time and not mix the oils. Personally I mix viscosities but not oil brands. And some oil types should'nt be mixed.

I wouldn't recomend anything but straight 30W dino oil for a non-turbo engine. I don't know much about turbochargers so I'd need to do some research to make that call. Depending on the turbo cooling and how it's related to the lube oil you may find the turbo dosn't heat the lube oil at all. Then the oil type and viscosity could be the same as a NA engine. If the turbo make very high temps and is cooled by the lube oil I would use a synthetic lube. If it's warmer than a NA engine but only slightly a synthetic blend and multi-viscosity 15W-40 would probably be good. Check the manual.

Shell Rotella and RPM Delo are of equal quality. Shell seems to be an east coast brand and Delo is very dominant especially in Alaska. Both excellent. For synthetic I don't know what's best. I have a bias against one brand but it has to do w ultralight aircraft 2 stroke application.

Ex Sailor,
Find out from Cummins before you change oil type or viscosity.

manyboats said:

I definitely would't do what the previous owner did ... unless you do your research and find that he was indeed using an oil that is 100% suitable for the engine. The previous owner may not have known enough to choose the right oil. Another exception is when the PO was using what the engine manual recommends. Most all the time you can't go wrong w the engine manual.

.

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AGREE - AGREE

My vote is manufacturer NOT previous owner - unless you've researched and agrees w/ mfg.

I would be cautious in changing with one regard. if you switch to an oil w/ high detergent after long use of non detergent type oil. from what i've read in the forum it could be a problem. Don't know firsthand thou.

No Mast,
I think the only non-detergent oil there is is The Dello stuff for Detroit Diesels. It's all more or less high detergent. The detergent thing is more or less a thing of the past.

manyboats said:

No Mast,
I think the only non-detergent oil there is is The Dello stuff for Detroit Diesels. It's all more or less high detergent. The detergent thing is more or less a thing of the past.

Click to expand...

good to know, thanks

It is very simple in my opinion: Use the formulation the engine manufacturer recommends. They typically publish oil specs in their shop manuals, ask a Cummins dealer.

caltexflanc said:

It is very simple in my opinion: Use the formulation the engine manufacturer recommends. They typically publish oil specs in their shop manuals, ask a Cummins dealer.

Click to expand...

Oh I agree