Yanmar - Mobil 1 Synthetic

[JackD]

I'm the new owner of a Mainship with Yanmar 6LYA-STP, 370HP. The owner's manual says I should use 15W-40 weight oil. The previous owner used 15W-50 Mobil 1 synthetic, which does not come in a 40 weight. Stick with the 50?

 

[bayview]

15W-40msynthetic diesel rated is available from many suppliers including Shell.


Why not use what the maker directs?
https://www.google.com/search?q=15w...&oe=&gws_rd=ssl#q=synthetic+diesel+oil+15w-40

 

[Nomad Willy]

I'd use the PO's oil.

Mobile 1 synthetic if it was/is formulated for diesel engines. The 15W50 viscosity is fine. Better almost certianly. Check w Yanmar to be sure. They may not have had 15W50 when the engine was made. They are a better source of information on what to do w a Yanmar than we are. Nice of you to ask though.

 

[TDunn]

Mobil 1 15W50 is S rated for gasoline engines. You need to use a C rated oil which is formulated for diesel engines. If you want to stay with a synthetic I suggest Shell Rotella T6 5W-40 synthetic. If you don't want to stay with a synthetic then any CJ rated 15W-40 will do. Good brands are Shell Rotella T, Chevron Delo 400, Texaco Ursa, etc.

 

[DavidM]

Why use a synthetic oil at all?


Synthetics have two primary advantages over a petroleum based oil: they have somewhat better lubricity compared with petroleum based multi grades and they don't oxidize as badly over time so they maintain their properties over a long period.


But petroleum based oils do just fine in the lubricity department and I suspect that you will never see any benefit during the life of the engine. Marine diesels don't wear out usually and never due to poor lubricity. Overloading, yes!


Secondly even ignoring manufacturer's recommendations, oil in diesel engines need to be changed to remove soot, fuel and replace lost additives, none of which is helped by having a synthetic. Sure big fleet operators test their oil and change it when those values get out of whack, but does a single boat operator want to do that, especially if it goes against the manufacturer's recommendations? So the low oxidation properties of synthetics is lost if you have to change the oil anyway.


But if you must use a synthetic I suspect there is no practical difference in Mobil 1's 15W50 and a petroleum based 15W40.


David

 

[FF]

The downside for synthetic in a recreational boat is hard to overcome.

Syntheic scrapes off and drains better , so it improves the mileage a tiny bit.

The hassle is they drain really well so the engine can get exposed to internal rust , and even dryer than normal cold starts.

Use the car or truck a lot , they do work, esp for ultra high loads in a high performance engine.

Use the boat once a month or so, there is no advantage.

On layup there is extra work required to seal the engine air tight.

 

[Marlinmike]

Not sure if it is still true of today, but back some Yanmar did NOT recommend synthetic oils.

 

[Nomad Willy]

I supported the synthetic oil and the MV only because the engine in question is a high output turbocharged engine presumably making lots of heat in the turbo.
That would be the only reason it would need ..
A. Synthetic oil (lube)
B. Multiviscosity ratings w MV additives.

Otherwise straight 30 or 40W oil would be best.

The only really significant advantage to synthetic oil is it's ability to perform well at very high temperatures. Synthetic is a lot better at dealing w heat. But the only place you'd find so much heat that the usual mineral (dino) oil may have trouble dealing w it is in high output turbocharged engines. No others.

But w the OP if he intended to run the engines hard I'd stick w the syn 15W50. I see he's a fisherman (sports) and most of them from what I read run really fast out to the fishing grounds.
If the OP was to run that boat more sedately .. say about 15 knots .. then I'd run 15w40 dino oil.

Just my opinion and in this case I'd call Yanmar.

 

[Donsan]

Mobil 1 15W50 is S rated for gasoline engines. You need to use a C rated oil which is formulated for diesel engines. If you want to stay with a synthetic I suggest Shell Rotella T6 5W-40 synthetic. If you don't want to stay with a synthetic then any CJ rated 15W-40 will do. Good brands are Shell Rotella T, Chevron Delo 400, Texaco Ursa, etc.

According to the product data sheet, Mobil 1 15W-50 meets the quality level of API CF.

Mobil 1™ 15W-50

 

[Capt.Bill11]

Use any diesel rated oil you want.

 

[TDunn]

According to the product data sheet, Mobil 1 15W-50 meets the quality level of API CF.

Mobil 1â„¢ 15W-50

I only found the SM rating when I looked. I note that your reference says "meets the requirements for CF", but doesn't say it is CF rated. That said CF is an old rating and CJ would be much better. If the engine is 1998 or newer the manufacturer likely called for CH or higher rating oil. Here is the info for CF rated oil.

CF Obsolete Service typical of indirect-injection diesel engines and other diesel engines that use a broad range of fuel types, including those using fuel with high sulfur content; for example, over 0.5% wt. Effective control of piston deposits, wear and copper-containing bearing corrosion is essential for these engines, which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service have been in existence since 1994 and may be used when API Service Category CD is recommended.

However, the statement of using C versus S rated oils stands.

 

[Donsan]

I only found the SM rating when I looked. I note that your reference says "meets the requirements for CF", but doesn't say it is CF rated. That said CF is an old rating and CJ would be much better. If the engine is 1998 or newer the manufacturer likely called for CH or higher rating oil. Here is the info for CF rated oil.

CF Obsolete Service typical of indirect-injection diesel engines and other diesel engines that use a broad range of fuel types, including those using fuel with high sulfur content; for example, over 0.5% wt. Effective control of piston deposits, wear and copper-containing bearing corrosion is essential for these engines, which may be naturally aspirated, turbocharged or supercharged. Oils designated for this service have been in existence since 1994 and may be used when API Service Category CD is recommended.

However, the statement of using C versus S rated oils stands.

I looked at the data sheet because I was wondering if using that product would result in harm to the engine. It convinced me it was unlikely to result in engine damage. Would I use it? No, I would stick to an oil that was designed for diesel engines (C service).

 

[bayview]

Generators and engines have turbos that can cook dino oil if not allowed to cool down prior to shut down. Syn oils are supposed to be better at that.


I don't ever remember reading about an lubrication caused failure of a boat engine. You could probably use the cheapest Wallyworld lube oil without any problems if you don't want to follow the makers advice, but why?

 

[gaston]

I spent many years in the "OIL" industry and I would prefer to change my petroleum based oil and filters twice for the same price of synthetic once .

Sorry no more comment

 

[what_barnacles]

Mobil also makes the mobil delvac which is a diesel specific oil. I havent priced it, but knowing mobil it probably costs a lot more than shells rotella T6 and probably not much better performance wise.

 

[Ski in NC]

50wt is some really thick stuff. No way I would want to spend my fuel dollars churning honey in the sump. Use what the mfr recommends.

 

[catalinajack]

Why use a synthetic oil at all?

Synthetics have two primary advantages over a petroleum based oil: they have somewhat better lubricity compared with petroleum based multi grades and they don't oxidize as badly over time so they maintain their properties over a long period.

But petroleum based oils do just fine in the lubricity department and I suspect that you will never see any benefit during the life of the engine. Marine diesels don't wear out usually and never due to poor lubricity. Overloading, yes!

Secondly even ignoring manufacturer's recommendations, oil in diesel engines need to be changed to remove soot, fuel and replace lost additives, none of which is helped by having a synthetic. Sure big fleet operators test their oil and change it when those values get out of whack, but does a single boat operator want to do that, especially if it goes against the manufacturer's recommendations? So the low oxidation properties of synthetics is lost if you have to change the oil anyway.

But if you must use a synthetic I suspect there is no practical difference in Mobil 1's 15W50 and a petroleum based 15W40.

David

No practical difference between a 40 grade and a 50 grade oil? Then why make two different grades? The difference is the viscosity at operating temperature. Engines are designed to use oils of a specific grade. Using a 40 grade oil in an engine designed to use a 30 grade is just the wrong way to go. Some folks believe that a higher grade oil is better to use in higher ambient temperatures because it stays thicker. Yes, at operating temperature it does stay thicker, thicker than what the engine was designed for. Remember, regardless of the ambient temperature, an engine, barring extremes boaters do not see, will run at its design temperature as regulated by the thermostat. That means the oil will be at the same viscosity at operating temperature REGARDLESS of the ambient temperature. Hence, using the 40 grade oil is not good. At operating temperature, the 40 grade will be too thick. And don't quote me Bob Smith. He is not a petroleum engineer. This is science folks.

 

[catalinajack]

The downside for synthetic in a recreational boat is hard to overcome.

Syntheic scrapes off and drains better , so it improves the mileage a tiny bit.

The hassle is they drain really well so the engine can get exposed to internal rust , and even dryer than normal cold starts.

Use the car or truck a lot , they do work, esp for ultra high loads in a high performance engine.

Use the boat once a month or so, there is no advantage.

On layup there is extra work required to seal the engine air tight.

Sorry to disagree, FF, but you have it 180 degrees off course on the properties of synthetic oil. You say that synthetics drain really well and leaving metal surfaces open to rust. Wrong. Wrong. Wrong. It is the dino oil that drains away and leaves surfaces dry. In fact, synthetics do just the opposite, they cling to metal surfaces, which is one the benefits synthetics offer that dino oils do not. Extra work to seal the engine? Poppycock! From where does this nonsense come?

 

[Nomad Willy]

catalinajack,
Thank you very much for clearing up this sticky subject.

gaston wrote;
"I spent many years in the "OIL" industry and I would prefer to change my petroleum based oil and filters twice for the same price of synthetic once ." Exactly.

ski,
50W as in 15W50? That's that the 15W50 oil has the viscosity of 50W oil at about 200 degrees ...... and at 200 degrees it's not thick at all. More like thin.

 

[dannc]

I'm the new owner of a Mainship with Yanmar 6LYA-STP, 370HP. The owner's manual says I should use 15W-40 weight oil. The previous owner used 15W-50 Mobil 1 synthetic, which does not come in a 40 weight. Stick with the 50?

I would stick with a 0Wx40, 5Wx40 or 15Wx40 oil.

My guess is that the previous owner could not find 15Wx40 oil and bought 15Wx50 oil instead. I have been buying oil for my truck and tractor from my JD dealer for the last few years, believe it or not, they had the best price most of the time. Last oil change I did not have time to get to the JD dealer so I looked at the local auto parts store and their price for Shell 0Wx40 diesel rated oil was pretty good and on sale.

Since it has been years since I bought oil from an auto parts store for my diesel, I was shocked at all of different motor oil weights now available. There were plenty of oils that appeared to be diesel oils, but on reading the labels, they were gas only. The diesel rated oil was on a completely different aisle and not near the gas motor oils. I suspect the previous owner missed the diesel rated oil...

Years ago, a big name motor oil company said they had a diesel rated oil and many people were paying top dollar for that oil for use in tractors and trucks. The company said the oil was diesel rated but the jug was not labeled as diesel rated. I think the company did not want to be pay to get the oil rated. Now, I would guess the oil was ok but given there are plenty of good oils out there that ARE rated for diesels, that is what I used then and now.

Use a diesel rated 15Wx40 oil at a minimum since that is what the manual says. I use synthetics for a variety of reasons but you can't go wrong using what the manual specifies and changing the oil per said manual.

Later,
Dan

 

[Baker]

No practical difference between a 40 grade and a 50 grade oil? Then why make two different grades? The difference is the viscosity at operating temperature. Engines are designed to use oils of a specific grade. Using a 40 grade oil in an engine designed to use a 30 grade is just the wrong way to go. Some folks believe that a higher grade oil is better to use in higher ambient temperatures because it stays thicker. Yes, at operating temperature it does stay thicker, thicker than what the engine was designed for. Remember, regardless of the ambient temperature, an engine, barring extremes boaters do not see, will run at its design temperature as regulated by the thermostat. That means the oil will be at the same viscosity at operating temperature REGARDLESS of the ambient temperature. Hence, using the 40 grade oil is not good. At operating temperature, the 40 grade will be too thick. And don't quote me Bob Smith. He is not a petroleum engineer. This is science folks.

While coolant temperature(your reference to the thermostat) does have an impact on the temperature of the oil, it is ultimately the efficiency of the oil cooler that determines the temperature of the oil. IOW, just because the coolant temp is 180 degrees does not mean the oil temp is the same. With that said, your point is taken. The oile temp will remain generally the same at normal operating loads. The only reason I bring this up the Yanmar in my previous boat had a very good oil cooler and I always had a hard time getting the oilt temp hot enough to change the damn oil. I could run the damn thing under full load and full throttle but I had to go thru a 5 minute no wake zone back to my slip and by the time I got there, the oil was cool to the touch. I could put the dipstick on the inside of my forearm without discomfort.....no s**t!!!!

 

[Ski in NC]

Yanmar 6ly series uses sea water oil cooler with no thermostatic control. The oil stays very cool, nowhere near the 200-220F that the coolant cooled oil coolers see, like Cat and Cummins and Detroit. Even cooler if running light load in cool sea temp. So with cool oil like that, the viscosity of most available oils will be way high. How high depends on each oil's temp vs viscosity curve.

If I was running a Yanmar at light load, I'd probably go with Rotella T 10w-30 dino oil. Provided that was ok per the manual specs.

There is no good reason to run a 15W-50 in a sea water oil cooled Yanmar in trawler service.

 

[timjet]

The predominant opinion on boatdiesel reflects David's comments above.

 

[what_barnacles]

There is no good reason to run a 15W-50 in a sea water oil cooled Yanmar in trawler service.

I agree with that but I would also add theres no good reason to not run 15-50 either. The 15 wt. rating is more than enough to allow full performance with a sea cooled engine.

I myself would tend towards Shells Rotella T with a 5-40 rating, but only to get the lower wt rating to let me go to the north pole before it melts.

 

[Peter B]

Use any diesel rated oil you want.

The voice of reason...ain't that the truth...God you guys are anal over oil...

 

[FF]

"Sorry to disagree, FF, but you have it 180 degrees off course on the properties of synthetic oil. You say that synthetics drain really well and leaving metal surfaces open to rust. Wrong. Wrong. Wrong. It is the dino oil that drains away and leaves surfaces dry."

When you tire of reading advertising hype , perhaps Googling long term engine storage ,

and also Vapour Phase Inhibitor oil.

reading http://www.cortecvci.com/Publications/Papers/05325.pdf will clear it up.

The simplest solution proposed would be to dip one bright nail in your synthetic and a second in whatever dyno oil you find.

Leave them out to rust for a few weeks,, ENJOY!

 

[Marlinmike]

Funny in my numerous (to many according to my wife) hobbies and most seem to have a combustion engine in it, all forums have the exact same debate and yet very little real empirical evidence from the average user.

 

[Ex Sailor]

We too just got our new ( to us ) boat with twin Cummins 210 HP @ 2500 hrs. on them and the boat came with a ton of Shell Rotella 15 - 40 oil. I am a fan of Synthetics but don't know if I should mess with what was used previously.

 

[TDunn]

You can't go wrong with Rotella T 15W40. It is the standard here on the Maine coast with the commercial boats.

 

[Bacchus]

Jack
You've touched on a hot topic - anchors next????

If you haven't seen it here's another oil related post w/ 100 +/- opinions

IMHO - The most informative article I've seen on the topic is the attached
Best Lubricants for Yacht Engines

I have decided to stick w/ Dino straight 30 wt rated CF-4 or CI-4 (but not the newer CJ-4). Based on the latest Yanmar recommendation I could find which is 2012.

and if you are looking for reading material I've compiled a list of related article links - also see attached - just noticed some of the links don't work - I'll attach the TDR 55 & 76 pdf's as well