engine oil - modern equivalent of CD standard

Tranona said:
Hardly a con. The point is not that sophisticated oils might do harm but that they are a waste. They are designed for engines that are totally different from our simple low powered engines. You don't need to go into the technicalities but logic says that an automotive engine that produces 2 or 3 times the power for size of engine, runs at 50% higher revs and has to cope with a duty cycle that includes high load cold starts, periods at idle, rapid acceleration and long high load runs needs a different type of oil than a yacht auxiliary that runs most of its life at half power at constant revs and temperature.
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Exactly my point. People are struggling to find suitable oil for elderly diesel when a readily available modern might do just as well.
 
oldmanofthehills said:
I just buy "oil for elderly diesel" for my 36yr old Bukh. The SAE range is better on some oils so if thinner when cold it will start better and thicker when hot it will cope with worn bearings and cylinder better so SAE10-40 is better for old and worn than SAE 20-30.
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Sorry, you are very confused here. The data given in the Bukh manual refers to monogrades of either SAE 20 or SAE 30. There is no such oil as an SAE 20-30. Multigrade oils carry the viscosity designation 15w-40 for example, probably the most appropriate one as a substitute for a monograde that has been superseded almost universally. I would most definitely not use a 10w-40 in a 36 year old Bukh. this cold viscosity is insufficient for a worn bearing and journal combination and you will increase wear rates at the critical time when the engine starts from cold. It is no mystery that oil for older engines sold by most manufacturers has 20w-50 viscosity.

However, there is more to an oil than its viscosity. You could usefully read the page on 'oil for yacht engines' on my website. Oils intended for engines running at high temperatures have high TBN to cope with the acids that are generated. In cool, raw water cooled engines these acids are barely generated at all, especially since fuel sulphur levels have been reduced so dramatically. Thus the oil will always be somewhat basic, which will tend to increase bore wear rates.
 
oldmanofthehills said:
Exactly my point. People are struggling to find suitable oil for elderly diesel when a readily available modern might do just as well.
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But it is not difficult to find suitable oil as it is available in every motoring shop and many supermarkets as this thread shows. The issue is uncertainty (as per the OP) on what is appropriate out of the choices available. There is no need to waste money on more sophisticated oils.

Of course there may come a time in the future when all the old automotive diesels have disappeared and high street demand falls and mineral oils become more scarce but we are a long way from there.
 
vyv_cox said:
Sorry, you are very confused here. The data given in the Bukh manual refers to monogrades of either SAE 20 or SAE 30. There is no such oil as an SAE 20-30. Multigrade oils carry the viscosity designation 15w-40 for example, probably the most appropriate one as a substitute for a monograde that has been superseded almost universally. I would most definitely not use a 10w-40 in a 36 year old Bukh. this cold viscosity is insufficient for a worn bearing and journal combination and you will increase wear rates at the critical time when the engine starts from cold. It is no mystery that oil for older engines sold by most manufacturers has 20w-50 viscosity.

However, there is more to an oil than its viscosity. You could usefully read the page on 'oil for yacht engines' on my website. Oils intended for engines running at high temperatures have high TBN to cope with the acids that are generated. In cool, raw water cooled engines these acids are barely generated at all, especially since fuel sulphur levels have been reduced so dramatically. Thus the oil will always be somewhat basic, which will tend to increase bore wear rates.
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Am I right in thinking that over-specified oils can be harmful, in that they don't provide sufficient lubrication at the low running temperatures of most of our diesels? And that is why you should use a CD or CF rated oil (assuming that's what the manufacturer recommends)?
 
Mr Cox your reply helps explain and be informative. I'm sorry I muddied the waters for you by saying SAE20-40 not 20 or 30, but what oil should I be using? I dont have my oil can from Trago Mills to hand as its on boat 150 miles away and thus I might mis-remember what it said on label but it said it was for elderly diesels and I am pretty sure it did not extend to SAE50
 
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oldmanofthehills said:
Mr Cox your reply helps explain and be informative. I'm sorry I muddied the waters for you by saying SAE20-40 not 20 or 30, but what oil should I be using? I dont have my oil can from Trago Mills to hand as its on boat 150 miles away and thus I might mis-remember what it said on label but it said it was for elderly diesels and I am pretty sure it did not extend to SAE50
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Most posts in this thread propose best practice. 15w-40 to API CF-4 is perfectly good for an old engine in reasonable condition. When oil consumption increases and bearings begin to be noisy, especially if oil pressure reduces (assuming you have a gauge) it is time to go to 20w-50. In my very elderly BMC 2.5 diesel, possibly 50 years old, I use 20w-50 to API CC bought from Morris Lubricants.
 
AntarcticPilot said:
Am I right in thinking that over-specified oils can be harmful, in that they don't provide sufficient lubrication at the low running temperatures of most of our diesels? And that is why you should use a CD or CF rated oil (assuming that's what the manufacturer recommends)?
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It sounds like it might be plausible but there is no scientific evidence for that hypothesis, only anecdotal tales. My personal experience is that provided you meet the viscosity requirements there is no technical disadvantage in using the best oil available. Of course, there will be a cost disadvantage which, for people who change the oil every year is significant. If you prefer to extend the oil change interval on the basis that the better quality oil retains its lubrication properties for longer, then the cost disadvantage reduces.

Others may well have a different opinion based on their different experience. :)

Richard
 
oldmanofthehills said:
I just buy "oil for elderly diesel" for my 36yr old Bukh. The SAE range is better on some oils so if thinner when cold it will start better and thicker when hot it will cope with worn bearings and cylinder better so SAE10-40 is better for old and worn than SAE 20-30.
.
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vyv_cox said:
Sorry, you are very confused here. The data given in the Bukh manual refers to monogrades of either SAE 20 or SAE 30. There is no such oil as an SAE 20-30. Multigrade oils carry the viscosity designation 15w-40 for example, probably the most appropriate one as a substitute for a monograde that has been superseded almost universally. I would most definitely not use a 10w-40 in a 36 year old Bukh. this cold viscosity is insufficient for a worn bearing and journal combination and you will increase wear rates at the critical time when the engine starts from cold. It is no mystery that oil for older engines sold by most manufacturers has 20w-50 viscosity.
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oldmanofthehills said:
Mr Cox your reply helps explain and be informative. I'm sorry I muddied the waters for you by saying SAE20-40 not 20 or 30, but what oil should I be using? I dont have my oil can from Trago Mills to hand as its on boat 150 miles away and thus I might mis-remember what it said on label but it said it was for elderly diesels and I am pretty sure it did not extend to SAE50
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vyv_cox said:
Most posts in this thread propose best practice. 15w-40 to API CF-4 is perfectly good for an old engine in reasonable condition. When oil consumption increases and bearings begin to be noisy, especially if oil pressure reduces (assuming you have a gauge) it is time to go to 20w-50. In my very elderly BMC 2.5 diesel, possibly 50 years old, I use 20w-50 to API CC bought from Morris Lubricants.
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The Bukh DV36 and DV24 are still manufactured (as is the DV29 and DV32). Whereas the original manuals referred only to monogrades, the current manual for the DV 36 & DV24 also lists multigrades (though still indicates API CC or CD):

LUBRICATING SYSTEM
TYPE OF LUBRICATING OIL PUMP ............... ROTARY VANE PUMP
LUBRICATING OIL PRESSURE: WARM ENGINE / MINIMUM ... 2-4.5 Bar / 1 Bar
LUBRICATING OIL QUALITY ..........................................SERVICE CC or CD
LUBRICATING OIL VISCOSITY....
BELOW +5oC ......................................SAE 10 or SAE 10W-30
BETWEEN +5oc and +25oC .................. SAE 20 or SAE 15W-40
ABOVE +25oC . .................................. SAE 30 or SAE 15W-40
LUBRICATING OIL CONTENT INCL. FILTER... 4.9 Litres (DV36), 3.5 litres (DV24)
LUBRICATING OIL FILTER .. ....................THROW AWAY FILTER INSERT
​
 
I do remember many years ago being told by a man who makes his living repairing and replacing boat engines that many owners love their engine to death using oil which is 'to good'. When I owned Galadriel I always used to find I could get API CD 10 - 40 mineral oil in French supermarkets probably for old 2CV's! I still have a 5 ltr can in the garage. Opie oils in Cornwall can supply an API CD oil, but its synthetic, perhaps Mr Cox would care to comment on the fact it is not mineral, Opie oils:

https://www.opieoils.co.uk/p-6504-motul-inboard-tech-15w-50-4t-boat-engine-oil.aspx

This oil from Morris is a SF/CD/CF mineral oil:

https://www.morrislubricants.co.uk/...-oils/ground-force-sae-10w-40-engine-oil.html

The French stuff used to be about 12 - 15€ a can, it might be worth stocking up on your next trip, if you can.
 
LittleSister said:
The Bukh DV36 and DV24 are still manufactured (as is the DV29 and DV32). Whereas the original manuals referred only to monogrades, the current manual for the DV 36 & DV24 also lists multigrades (though still indicates API CC or CD):

LUBRICATING SYSTEM
TYPE OF LUBRICATING OIL PUMP ............... ROTARY VANE PUMP
LUBRICATING OIL PRESSURE: WARM ENGINE / MINIMUM ... 2-4.5 Bar / 1 Bar
LUBRICATING OIL QUALITY ..........................................SERVICE CC or CD
LUBRICATING OIL VISCOSITY....
BELOW +5oC ......................................SAE 10 or SAE 10W-30
BETWEEN +5oc and +25oC .................. SAE 20 or SAE 15W-40
ABOVE +25oC . .................................. SAE 30 or SAE 15W-40
LUBRICATING OIL CONTENT INCL. FILTER... 4.9 Litres (DV36), 3.5 litres (DV24)
LUBRICATING OIL FILTER .. ....................THROW AWAY FILTER INSERT
​
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Morris do a 10 - 40 CC
 
Topcat47 said:
Comma do a basic 15:40 mineral oil. i get it from my local Motor Factors. They also do a classic oil 20:50 but it's more expensive and aimed at petrol engines (I use it in the Morris 1000).
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+1 my motor factor does it in 5litre and 1litre bottles. I need 5.9litres. £16.38 inc Vat.

Donald
 
SAWDOC said:
Popped into Halfords today - the classic car oil they stocked was 20w 50 API SE CC.
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That is different from the oil they sell for diesel engines. The oil you saw is for old petrol engines from the 50s and 60s such as Morris Minors somewhat like the Duckhams we all used to swear by in those days!
 
I use synthetic oil for my VP MD11C. Nowadays, Synthetic oils are superior in every way. My engine is old but runs great and it starts on the button; I change oil and filter every year for the past 12 years.
 
Sans Bateau said:
I do remember many years ago being told by a man who makes his living repairing and replacing boat engines that many owners love their engine to death using oil which is 'to good'. When I owned Galadriel I always used to find I could get API CD 10 - 40 mineral oil in French supermarkets probably for old 2CV's! I still have a 5 ltr can in the garage. Opie oils in Cornwall can supply an API CD oil, but its synthetic, perhaps Mr Cox would care to comment on the fact it is not mineral, Opie oils:

https://www.opieoils.co.uk/p-6504-motul-inboard-tech-15w-50-4t-boat-engine-oil.aspx

.
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I cannot find any further data about it. I assume that for an API CD oil the TBN is low, somewhere around 3-4. As the page on my website says there is nothing inherently wrong with a synthetic base oil - indeed it has excellent properties. If this Opie oil is a genuine Grade 4 synthetic with additives to API CD it should be the answer to everyone's question.
 
Sans Bateau said:
I do remember many years ago being told by a man who makes his living repairing and replacing boat engines that many owners love their engine to death using oil which is 'to good'.
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Indeed. As I said above "there is no scientific evidence for that hypothesis, only anecdotal tales".

If you can find a synthetic oil with the correct viscosity then, cost aside, in my experience it's going to be better for your engine than the equivalent mineral grade. :)

Richard
 
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