Yanmar 3GM30 running well but using a lot of oil.

[a64pilot]

If you think it’s glazing, I have seen quite a bit of success from running them hard and running a detergent additive in the oil along with a high detergent oil of course, usually most higher grades of oil are high detergent. Sea Foam or ATF, ATF is good but not really aggressive like Sea Foam apparently is.
Worst case is you clean out your oil system is all.

[Compass790]

You can try this oil to reduce consumption. It has the CD rating if you are fixated on that & it has the benefit of being both less viscous than straight 40 when cold & more viscous when hot. It's made for engines with excessive clearances.
https://penriteoil.com.au/products/c...25w-70-mineral

Good that your consumption seems to be getting less with the hard runs.If consumption remains too high I'd try the valve stem seals next as that is the easiest possible cause although my suspicion is oil control rings.

[NotEntirelySure]

I quick catch up post. Engine still running fine with more or less the same fairly hideous consumption at around 85 - 90ml per hour. Took the vessel north to the Whitsundays (and back to Brisbane) for a couple of months late last year and clocked about 150 hours in the process. Ran like a clock too. Had to dump the straight 30 grade oil prematurely as it actually used a bit more with this oil and seemed to flog out earlier (and consumption went up to around 130ml and hour). Back to Castrol XLD and for the moment I guess just keep topping it up every 5 hours.

If I could find the heavier grade Penrite somewhere I would probably give it a try. Seems to hard to locate at the moment.

Thanks again to everybody on their input and I will report back when I ultimately pull it apart. Hoping to get another trip north this year though without a rebuild prior.

[Compass790]

Thanks for update, always good to hear whats happening.

Not at all surprised that your oil consumption went up using straight 30. It never seems to sink into peoples heads how a multigrade works. In short your 20w-50 is thicker at operating temp than straight 30 therefore should leak less.
Dont worry about doing another trip if oil pressure is ok & engine running fine as well as not being not too noisy. As stated many times previously lots of engines run for decades using oil.
Did you try A64's tip re seafoam?

[NotEntirelySure]

Originally Posted by Compass790

Thanks for update, always good to hear whats happening.

Not at all surprised that your oil consumption went up using straight 30. It never seems to sink into peoples heads how a multigrade works. In short your 20w-50 is thicker at operating temp than straight 30 therefore should leak less.
Dont worry about doing another trip if oil pressure is ok & engine running fine as well as not being not too noisy. As stated many times previously lots of engines run for decades using oil.
Did you try A64's tip re seafoam?

Haven't tried seafoam or equivalent. Engine sounds sweet and performs well hence haven't done a compression check. Will probably do one soon when I give the engine a service. I had reservations about the old school 30 grade oil but when you have a number of old hands tell you that's the go for that engine you have to try it I suppose even if theoretically it makes no sense. I'll report back once I try a heavier oil, currently Castrol RX super 15/40 not what I quoted above.

[Compass790]

Yea it probably doesnt have a compression issue if it starts easy but sometimes, on a multi cylinder, its hard to tell. Its more likely oil control ring or v/v seals but good to check. Anyway when you pull the injectors for test you'll see if ones oily.

You should be able to get 20w- 50 or 60 ok even if you cant find the 25w-70.
We can get it from supercheap auto in NZ so I'm sure you can get it in Brizzy.
Changing frm 15w-40 to 20w-50 upped the oil pressure by 5lb hot in our Yammer just as an aside. Not sure how much difference in consumption it will make but worth a try I reckon. The 20w-50 Gulf western is often real cheap too if money is a factor.