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Old 13-01-2012, 19:17   #16
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Re: synthetic oil

Originally Posted by Jon Hacking View Post
Thanks, Delmarray. I didn't know that either. Now I read that Yanmar engines actually want mono-grade 40, not a multi-vis. We've got 4JH2CE engines w/6K hours & I've been using 15w40. Is that a problem?

We're also considering going with an external toilet-paper type oil filter as well as the spin-on. I can never get the last bit of oil out of the dip-stick tube, & that has much of the grunge in it, so our oil turns black quickly after a change. The TP filter should cure that, so I was thinking of switching to a synthetic, but now I realize that's not a good idea.
Recommended oils for Yanmar Engines.

For an outstanding article on oil by AMS Oil follow the link below:

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Old 13-01-2012, 19:37   #17
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You can also flush the last bit of crud out with some clean oil.


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Old 13-01-2012, 19:43   #18
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Originally Posted by s/v Jedi
You can also flush the last bit of crud out with some clean oil.

+1, this is what I do. I use 1.5 quarts I have from the previous year's "spares" to flush the system. I figure year old clean oil is better than 2 year old dirty oil.

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Old 13-01-2012, 19:51   #19
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Re: Synthetic Oil

Originally Posted by casual View Post
I am purchasing a new used boat.The yard where the boat is at only uses synthetic oil,The engin is a Yanmar 4JH3E appx 3000 hours,I have no knowledge of PO oil type,Will synthetic oil do is it better than Castro GTX which I have always used in my present Boat?I am sure I could get some Castro oil somehow.This engin was making oil due to a bad lift pump,had oil analysis done all ok.Thanks for the help,PS this will be the first change after analysis
I'm convinced that synthetics are better oils for two reasons :

1) They retain their viscosity for longer (more use that is, not time)

2) They hold their viscosity over a wider range of temps.

However I don't think either of these are of much benefit in a sailboat diesel, when the oil will probably be changed for time-expiry and not hours operation.

They make the most financial sense when you can take advantage of the longer life.

I suspect that ANY 15w/40 with a diesel rating will do fine. I used Shell Rotella which is very popular with truck fleets. It comes in normal, semi-synthetic, or full. It's also available at Wal-mart quite cheaply and comes in 1 gal bottles instead of those stupid 1 quart ones so you've got something to pour the used oil into!
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Old 13-01-2012, 21:07   #20
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Re: Synthetic Oil

I tryed Rotella In 15/40 when I changed engines in my last boat,went from Volvo to Lehman, seemed ok for a couple of changes then I could not get some so went back to my old stand by Delo 15/40, saw an instant rise of oil pressure 5 lbs at Idle, and almost 10 lbs at cruise , had to reset idle as after at couple of hours running the idle was a little to fast! of course it was still brand new the increse in idle mite just be normal Ive had this happen before but the oil pressure has stayed higher then before! I think Im gonna stay with Delo. Bob and Connie
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Old 06-08-2012, 03:13   #21
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Re: Synthetic Oil

At least one engineer (in this case, a real professional petroleum/lubricant engineer who happens to be a sailor) believes that synthetic oil is positively harmful to marine diesel engines. See: Oil for yacht engines

It is my recollection (although I couldn't find a reference just now) that Yanmar discourages the use of synthetic oil in their diesel engines.
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Old 07-10-2012, 14:25   #22
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Re: Synthetic Oil

I just bought 2003 Sea Ray with twin 350 MetCruisers. It had a synthetic oil change and now has only 15 hours on it and is headed for indoor storage for the winter. Do I need to change the oil again in the spring?
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Old 08-10-2012, 20:59   #23
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Re: Synthetic Oil

Good article. Though it addresses the additive package as the potential hazard rather than the base oil construction. What I gather from the text is that the synthetic oil base is superior to the mineral oil base but you have to watch whatever bling goes into it and for what purpose. When I buy oil I look for a small delta between the low and high numbers in the multigrade spec. (15-40 is my choice in my part of the country). This means fewer viscosity modifiers in the mix.

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