Yanmar 3YM30 oil?

[malbert73]

So I am a bit confused. I went to change my oil at end of season on my 3YM30 (600 total hours) and the local yanmar dealer in Baltimore tells me that they are now recommending Yanmar 30 weight oil for the engine. They even had a big yanmar desk chart with all their engines and the reference oil, and sure enough- 30 weight oil.

Anyone else doing this? my first 4 seasons with engine I went with recommended 15W/40.

[YankeePSC34]

Is 30 usually not cheaper than 15W40? Save a buck!

[Freerider]

Depends on the climate, I run Rotella T6 which is a 5w-40 synthetic. Makes for easier starting on cold days.

When looking at oil manufacturers' top synthetic oils for diesel, they are usually multi-grade in a 40 weight at operating temperature.

Starting a diesel in sub-zero temperature with a straight 30 is tough, and can cause severe wear on the cylinders over the long haul.

[YankeePSC34]

I was mistaken. The price for SAE 30W and SAE 15W-40 is the same. Since you are sailing in the Baltimore area both oil grades should be acceptable. I don't see the reason why the Yanmar folks in Baltimore nail it on SAE 30W nowadays.

However Rotella T6 synthetic oil cost nearly the double. It would be interesting to hear from boaters who are using it, if they are also stretching the operating hours between the oil changes.

[Ziggy]

As far as I know, Yanmar still recommends multigrade oil (15W40 or 10W30) for the 3YM30 engines.

Edit: The temperature inside your engine compartment could easily reach well over 90F, so I'd go with 15W40.

[a64pilot]

I've been building Diesels and maintaining them for years, spend the couple of extra bucks for the Rotella syn, do not extend the oil change intervals, at least not the hourly ones, calendar maybe. Reason is it's extremely uncommon for Diesel engine oil to suffer any significant breakdown as long as it's changed on schedule. You change Diesel oil when it essentially gets so loaded with contaminates that it needs it, not because it's breaking down. I feel pretty sure the recommendation for straight 30W is for people that don't change their oil when they should. The further the spread in viscosity for a regular oil, the more it depends on it's additive package to get that, the additive package is what breaks down first, causing oil that is overdue it's change by a wide margin to lose it's viscosity. Synthetic oils commonly don't need additives to have a wide spread in temperature range, hence no additive package to break down. It's only one reason sometimes synthetics are superior. Having said all of this, if you maintain your engine like you should, run it like it should be run, change oil regularly etc. I think you may go as far as 10,000 hours on an engine running regular oil, just Syn give you a little cushion for those times when you should change your oil, but can't, plus I'm convinced from engine teardowns that it does cause less wear, but some of this may be due to the fact that a person that will spend more on their oil, may be more likely to properly care for an engine than someone that doesn't.

[djmarchand]

Originally Posted by a64pilot

I'm convinced from engine teardowns that it does cause less wear, but some of this may be due to the fact that a person that will spend more on their oil, may be more likely to properly care for an engine than someone that doesn't.

A classic case of mixing up cause and effect. I agree that those who use synthetic oil, take better care of their engines.

David

[Peter Gazzard]

I have a 3JH5E yanmar diesel and I use 15 w/40 multi grade engine oil and change the oil ever 250 hours. Am I doing it to often.Your expert thoughts please!