Older Marine Diesel - What Oil?

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Babylon

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Engine is a 28 year old Bukh DV20, which is using moderate amounts of oil (lots of little leaks rather than burning it, nothing catastrophic, just means I have to keep topping up, about 0.5 litre of oil every 15 running hours at 70% revs, more frequently if have to give it some welly to punch through a chop).

I've been topping up with 15W40, but should I be using HD30 - a thicker oil for older naturally-aspirated diesel engines - or doesn't it make any real difference?

Thanks
 
Babylon said:
I've been topping up with 15W40, but should I be using HD30 - a thicker oil for older naturally-aspirated diesel engines - or doesn't it make any real difference?
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This subject attracts the same polarised views as anchors! I think Bukh recommended 20 grade for our sort of temperatures. I can't imagine that using 15W40 will do it any harm. The argument that modern, sophisticated multigrade oils are somehow harmful to old engines is one I don't follow.
 
try using 20w40 next time you have to get some more supplies of oil and see how it goes, most of the newer engines have a recommendation of 15w40 nowadays. but i dont think there is to much difference in it, the experts will be along in a minute to shoot the recommendations down in flames, so just wait a couple of hours and you will be totally confused.(not what you really need to hear).
 
Babylon said:
Engine is a 28 year old Bukh DV20, which is using moderate amounts of oil (lots of little leaks rather than burning it, nothing catastrophic, just means I have to keep topping up, about 0.5 litre of oil every 15 running hours at 70% revs, more frequently if have to give it some welly to punch through a chop).

I've been topping up with 15W40, but should I be using HD30 - a thicker oil for older naturally-aspirated diesel engines - or doesn't it make any real difference?

Thanks
Click to expand...

Asda or B&Q 15>40 at around a tenner per 5 lts
 
Like PVB I find it difficult to follow the arguments against using modern oils in older engines. ( I am glad I am not alone !)

However Vyv Cox is the resident expert and there is a section on his website that deals with the issues.

http://coxengineering.co.uk/

He knows more about the subject than I do so I respect his advice even though I do not understand the logic!
 
I always use the older type oil as my engines are 30 year old mercs. Nevertheless I would use modern oils but would not mix oils,once I put in whatever, I stay with it until the next oil change. Its possible the oils today would be inter changeable but being an old belt and braces type I dont chance it. Why not get some gasket sealant and cure some of your leaks?
 
"If you used a thicker oil you might get less leakage. 20W50?"

I wondered that and once tried a straight 30, but found that it made no significant difference. In our 35 year old Volvo, we use Lidl's el-cheapo oil for diesel engines, bought in bulk whenever we find it on offer; no problems so far.
 
A retired Strathclyde Police Officer who was very senior and involved in driving and examining their examiners advised me of tests that they had carried out on oils for their cars. This was 1985. The test involved bearings under load and lubricated with various oils. The best oil they found was a B and Q 20/50 which out performed many of the heavily advertised performance oils of the time.

Of course today we are 25 years down the line but I dont think that old engines are so sensitive that they will go tits up at a whiff of the wrong oil. Then again the devil is always in the detail.
 
Topping up with a different grade altogether?

VicS said:
Like PVB I find it difficult to follow the arguments against using modern oils in older engines. ( I am glad I am not alone!) However Vyv Cox is the resident expert and there is a section on his website that deals with the issues. http://coxengineering.co.uk/ He knows more about the subject than I do so I respect his advice even though I do not understand the logic!
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Vic

Thanks for this link to Vyv's site. Boiled down, what he's saying is that you should indeed use older oils for older engines. I've found a monograde SAE30 oil to API classification CC, which Vyv's table says is in fact obsolete and shouldn't be used in engines built after 1990, but sounds just the thing for my engine.

The next question is, mid-season, should I change the oil to this SAE30 completely (but leave other engine items alone pending a service at the end of the season), or just start topping up with the 'new' SAE30 rather than the 'old' 15W40 as I go along? Or is this very bad practice?
 
As some of the later oils are either synthetic or semi synthetic,its hard to know whether they will mix or not. I was told some time ago that they can gel up if mixed, but cant say for definate better to be safe than sorry and change oils and filter. N
 
higler said:
I always use the older type oil as my engines are 30 year old mercs. Nevertheless I would use modern oils but would not mix oils,once I put in whatever, I stay with it until the next oil change. Its possible the oils today would be inter changeable but being an old belt and braces type I dont chance it. Why not get some gasket sealant and cure some of your leaks?
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Already dealt with the more accessible gaskets etc, but one of the major culprits is I think the front seal - which will have to wait until the end of the season, so I'm in top-up mode for now (or, as you suggest is good practice, change the oil competely to the SAE30 and top-up with the same).

Thanks for the feedback.
 
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Babylon said:
I've been topping up with 15W40, but should I be using HD30 - a thicker oil for older naturally-aspirated diesel engines - or doesn't it make any real difference?

Thanks
Click to expand...

At operating temperature the 15w40 is thicker than the HD 30. 40 is greater than 30. But when cold it is thinner which allows the oil to circulate better when all the wear is occurring.

Only thing to avoid with an old engine is the word "synthetic" - and that's advice from the tech dept at Castrol.
 
Babylon said:
Engine is a 28 year old Bukh DV20, which is using moderate amounts of oil (lots of little leaks rather than burning it, nothing catastrophic, just means I have to keep topping up, about 0.5 litre of oil every 15 running hours at 70% revs, more frequently if have to give it some welly to punch through a chop).

I've been topping up with 15W40, but should I be using HD30 - a thicker oil for older naturally-aspirated diesel engines - or doesn't it make any real difference?

Thanks
Click to expand...

Although it sounds like you should be trying to figure out how to stop the leaks, rather than which oil might help, I will offer this advice:
1/ Use a thicker oil like a 20w50, unless it gets too cold.
2/ Change to an oil that has lots of seal conditioners. The best thick one is Mobil 10w60 EL, (Not EP which is a race oil), although cheaper Castrol GTX 15w40 also contains seal conditioners.
3/ If that does not reduce the drip rate, then as a last ditch measure, add a can of Liqui Moly Stop Leak, (Called Motor Oil Saver).
4/ Change the oil more often, as part of the problem might be caused by fuel contamination thinnning the oil.

Note: There is very little difference between a 15w40 and a straight 30 grade after a few thousand miles. The reason is that multi grade oils contain viscosity improver additives that make the oil more prone to high temp shearing. That side effect means a multigrade will thin down faster than a single grade oil.

Old diesels like lots of Zinc based anti wear additives, so it's best to stick to major brand oil companies to make sure they are part of the oils additive package. By major brand I mean, Liqui Moly, Mobil, Shell, Castrol and any dealer specific companies, which means including Morris oils. Some people would also include Valvoline, Millers and the new, born again Duckhams.
 
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Holy cow; you really won't stop until you've created zombies out of every dead thread that mentions Bukh. Check the date of the last post next time?
 
Nothing wrong with an old post, in fact they are far better than new posts, as they have had time to mature!
 
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