engine oil - modern equivalent of CD standard

[Sans Bateau]

doesnt modern spec oil "incorporate" all old lower preceded specs, or have i got this wrong

There does appear to be opposing views on this, you have to judge for yourself. But I would always use an oil which the original manufacture intended. For instance, a 5/40 fully synthetic is perfect for my hi tech car manufactured in 2016, but a basic mineral 25/50 is all I will put in my classic car and no way would anyone I know use a hitech oil. There are any number of engine oil manufactures making everything from a 30 or 40 weight mono grade oil to the 20/50 I mention for classic cars of all ages, they do so for a reason, but then there is a bigger market than marine engines where the choice is limited.

I took advice the of a professional, who witnesses the result of DIYers using hitech modern oil in an old design engines, he could have sold me either at the time, he didnt. Its your decision.

 

[sailorman]

There does appear to be opposing views on this, you have to judge for yourself. But I would always use an oil which the original manufacture intended. For instance, a 5/40 fully synthetic is perfect for my hi tech car manufactured in 2016, but a basic mineral 25/50 is all I will put in my classic car and no way would anyone I know use a hitech oil. There are any number of engine oil manufactures making everything from a 30 or 40 weight mono grade oil to the 20/50 I mention for classic cars of all ages, they do so for a reason, but then there is a bigger market than marine engines where the choice is limited.

I took advice the of a professional, who witnesses the result of DIYers using hitech modern oil in an old design engines, he could have sold me either at the time, he didnt. Its your decision.

An engine gets older from day one, on the other hand oils from that same date get improved rending those oils recommended, obsolete

 

[vyv_cox]

Thanks. Yes, I saw that link at your #30. I have steered clear of synthetics, which have tended to have the later API specifications anyway. But I saw Vyv Cox’s response at #36 to your question, saying that synthetic was not necessarily a problem and that it might be an answer to those seeking a low TBN CD oil. But I also saw that he could not find any more information about it.

BTW As far as I can see – but I might be wrong, and would welcome clarification from Vyv or somebody else - API grades have not specified TBN. If that is so, have TBN ranges been attributed to the API grades on the basis of their other characteristics?

You are correct, TBN is not in the API spec. There are clues in it but you need to look at example data sheets to be sure.

 

[John100156]

Very interesting thread this, but what I don't quite get is what causes the generation of acids in the oil? Is it just excessively high temps, causing breakdown at molecular level? Is it when the oil is burned but surely any oil that manages to pass the rings or valve stems would be burned/exhausted. I am genuinely interested.

 

[RichardS]

Very interesting thread this, but what I don't quite get is what causes the generation of acids in the oil? Is it just excessively high temps, causing breakdown at molecular level? Is it when the oil is burned but surely any oil that manages to pass the rings or valve stems would be burned/exhausted. I am genuinely interested.

In general , the oxidation products of metal are alkaline and the oxidation products of non-metals are acidic. The major component of oil are carbon, hydrogen and sulphur which are all non-metals so the oxidation products formed by the high temperatures and pressures found in internal combustion engines tend to be acidic. However, at worst, these are weak acids in very low concentrations so the additives in oil which are designed to neutralise the acidity have a very modest role to perform.

Oxidised oil sticks to the bores and escapes past the valve stems so does end up mixing with the oil in the sump.

Richard

 

[John100156]

Thanks Richard that makes sense to me and I understand from the component parts the type of acid that may be created, most interesting, sorry to OP for thread drift...

 

[Hydrozoan]

Exhaust gas recirculation as a NOx emission reduction technique in modern automotive engines will also increase oil acidity.

 

[ronmarson]

SAWDOC,
Will you please stop opening cans of worms.
Capt. RoN

 

[ctva]

I used to be happy with a simple diesel mineral oil for a Yanmar 3GM... However my old supply has just run out after winterising the boat yesterday. My new choice is G-Force 15W-40 made by Carlube 15W-40 and the blurb says "is suitable for use in most modern petrol engines including naturally aspirated and turbo-charged vehicles with multi-valves, fuel injection and twin-cams. Also suitable for light duty diesel applications. PERFORMANCE LEVEL • API SL • ACEA A3/B3, A3/B4"

Will this be ok?

(and I thought anchor threads were contentious... )

 

[RichardS]

I used to be happy with a simple diesel mineral oil for a Yanmar 3GM... However my old supply has just run out after winterising the boat yesterday. My new choice is G-Force 15W-40 made by Carlube 15W-40 and the blurb says "is suitable for use in most modern petrol engines including naturally aspirated and turbo-charged vehicles with multi-valves, fuel injection and twin-cams. Also suitable for light duty diesel applications. PERFORMANCE LEVEL • API SL • ACEA A3/B3, A3/B4"

Will this be ok?

(and I thought anchor threads were contentious... )

That's a semi-synthetic and is the same spec as the 15W-40 semi-synthetic that I use for my YM Yanmars except mine is from Halfords, although it's possibly exactly the same manufacturer.

(There you go .... not so contentious after all. :encouragement

Richard

 

[vyv_cox]

Very interesting thread this, but what I don't quite get is what causes the generation of acids in the oil? Is it just excessively high temps, causing breakdown at molecular level? Is it when the oil is burned but surely any oil that manages to pass the rings or valve stems would be burned/exhausted. I am genuinely interested.

They are known as 'weak organic acids' and result simply from the burning of fuel in air. Some are carbonic, nitronic, sulphonic, sulphamic and no doubt there are others. The main problem caused by these acids in the lubricating oil is that they attack lead. Copper-lead bearings with lead-tin or lead-indium overlays are pretty much universal in diesel engines. These will corrode badly and fail if the acids are not neutralised. There are other problems but corrosion is probably the main issue. Automobile manufacturers have tried to overcome this partly by specifying aluminium-tin bearings but these need hardened shafts and are not well suited to diesels.

Hotter engines, and those running on lower quality fuels, produce more of these acids and hence need a higher TBN to neutralise them. High performance automobile oils have a TBN of around 12 - 15 and I once worked on very large ships' engines that used an oil with a TBN of 80.

 

[ctva]

That's a semi-synthetic and is the same spec as the 15W-40 semi-synthetic that I use for my YM Yanmars except mine is from Halfords, although it's possibly exactly the same manufacturer.

(There you go .... not so contentious after all. :encouragement...

Thanks for the info but It’s not semi-synthetic, it’s mineral.

 

[John100156]

They are known as 'weak organic acids' and result simply from the burning of fuel in air. Some are carbonic, nitronic, sulphonic, sulphamic and no doubt there are others. The main problem caused by these acids in the lubricating oil is that they attack lead. Copper-lead bearings with lead-tin or lead-indium overlays are pretty much universal in diesel engines. These will corrode badly and fail if the acids are not neutralised. There are other problems but corrosion is probably the main issue. Automobile manufacturers have tried to overcome this partly by specifying aluminium-tin bearings but these need hardened shafts and are not well suited to diesels.

Hotter engines, and those running on lower quality fuels, produce more of these acids and hence need a higher TBN to neutralise them. High performance automobile oils have a TBN of around 12 - 15 and I once worked on very large ships' engines that used an oil with a TBN of 80.

Hi Vyv, thanks: What I suppose I am trying to understand is if the mild acids created due to the burning off of 'fuel' I assume with miniscule amounts of oil in air (its been MANY years since I did 'manual' stoichiometric combustion calcs, but I understand that process) then any 'engine oil' burnt with the fuel in the combustion chamber, the products of combustion would surely be discharged through the exhaust manifold? So how do they then contaminate the oil in the engine and damage the bearings? Would not the piston rings and scraper ring prevent this? Or is it the heat created in the pistons that causes the breakdown?

 

[Sans Bateau]

They are known as 'weak organic acids' and result simply from the burning of fuel in air. Some are carbonic, nitronic, sulphonic, sulphamic and no doubt there are others. The main problem caused by these acids in the lubricating oil is that they attack lead. Copper-lead bearings with lead-tin or lead-indium overlays are pretty much universal in diesel engines. These will corrode badly and fail if the acids are not neutralised. There are other problems but corrosion is probably the main issue. Automobile manufacturers have tried to overcome this partly by specifying aluminium-tin bearings but these need hardened shafts and are not well suited to diesels.

Hotter engines, and those running on lower quality fuels, produce more of these acids and hence need a higher TBN to neutralise them. High performance automobile oils have a TBN of around 12 - 15 and I once worked on very large ships' engines that used an oil with a TBN of 80.

Vyv, I have not seen (I may have missed it) any discussion about the lack of zinc, ZDDP, in modern synthetic oils, surely older marine engines wont have roller tappets, or even OHC's running in an oil bath. Found this on Wiki:

"Crankcase oils with reduced ZDDP have been cited as causing damage to, or failure of, classic/collector car flat tappet camshafts and lifters which undergo very high boundary layer pressures and/or shear forces at their contact faces, and in other regions such as big-end/main bearings, and piston rings and pins. Roller camshafts/followers are more commonly used to reduce camshaft lobe friction in modern engines."

 

[Graham376]

Just to confuse the issue, Thornycroft instructions for my Mitsubishi base engine are to use CD mineral oil, which I have been doing. Just had a look at Mitsubishi site where I found two manuals/spec sheets for this engine. One says - Recommended Oil CD/CE/CF 10W/40 grade semi-synthetic or synthetic. The other says - Use oils that meet the Engine Service Classification CF or CF-4 and, according to the temperature tables, SAE 30, 40 or 15-40 are all suitable.

P.S. These base engines are often used at fairly high constant revs. driving hydraulic pumps in plant whereas boat engines are generally used at lower revs and for much shorter periods. Does this have any effect on choice of oil?

 

[RichardS]

Thanks for the info but It’s not semi-synthetic, it’s mineral.

Ah .... you didn't say that so I just did a Google search for what you did say and the first hit was: https://www.ebay.co.uk/p/G-force-15...-Motor-Engine-Oil-20ltr-20-Litres/24007494694

The semi-synthetic version would be better but if you have the mineral version then that will also be fine.

Richard

 

[RichardS]

Hi Vyv, thanks: What I suppose I am trying to understand is if the mild acids created due to the burning off of 'fuel' I assume with miniscule amounts of oil in air (its been MANY years since I did 'manual' stoichiometric combustion calcs, but I understand that process) then any 'engine oil' burnt with the fuel in the combustion chamber, the products of combustion would surely be discharged through the exhaust manifold? So how do they then contaminate the oil in the engine and damage the bearings? Would not the piston rings and scraper ring prevent this? Or is it the heat created in the pistons that causes the breakdown?

Just replace the "oil" in my post #65 with "fuel" as the two majority chemical compositions are interchangeable and similar oxidation products end up in the sump in the same way whether they came from oil or fuel combustion.

I would also imagine that some oil degradation occurs at the hotspots on the underside of the piston crown as this area is always encrusted with black carbon particulate deposits on an engine which has been run on mineral oil. In my experience, an engine run on synthetic oil does not exhibit this build-up because of the higher temperature stability of synthetics. Whether that lower temperature source of degradation of oil, rather than actual combustion, also produces acidic by-products, I do not know.

Richard

 

[vyv_cox]

Hi Vyv, thanks: What I suppose I am trying to understand is if the mild acids created due to the burning off of 'fuel' I assume with miniscule amounts of oil in air (its been MANY years since I did 'manual' stoichiometric combustion calcs, but I understand that process) then any 'engine oil' burnt with the fuel in the combustion chamber, the products of combustion would surely be discharged through the exhaust manifold? So how do they then contaminate the oil in the engine and damage the bearings? Would not the piston rings and scraper ring prevent this? Or is it the heat created in the pistons that causes the breakdown?

This seems to be the 'perfect seal' discussion again. I think you are correct that most of the combustion product goes down the exhaust pipe but some of it certainly does not. It may be that some of the acids condense on the bores but what is certain is that the lubricant will steadily become more acidic. The bores are coated with a film of oil that does not burn but is transferred into the sump by the pumping action of the rings moving in their grooves.

My ex-boss was one of a team from Shell Research who sampled lubricant below the top piston ring in a running engine and demonstrated increase in acidity. Link to a one-page summary here https://www.york.ac.uk/res/gkg/posters/add03.ppt

 

[vyv_cox]

Vyv, I have not seen (I may have missed it) any discussion about the lack of zinc, ZDDP, in modern synthetic oils, surely older marine engines wont have roller tappets, or even OHC's running in an oil bath. Found this on Wiki:

"Crankcase oils with reduced ZDDP have been cited as causing damage to, or failure of, classic/collector car flat tappet camshafts and lifters which undergo very high boundary layer pressures and/or shear forces at their contact faces, and in other regions such as big-end/main bearings, and piston rings and pins. Roller camshafts/followers are more commonly used to reduce camshaft lobe friction in modern engines."

Not my subject I'm afraid. I have lots of experience with synthetics in machinery, where it has virtually no additives at all. Many case histories demonstrate that its lubricity is remarkable, solving many lubrication problems in highly loaded applications. It may well be that this property assists in cam/tappet lubrication, allowing ZDDP reductions but I am only guessing.

 

[RichardS]

Many case histories demonstrate that its lubricity is remarkable, solving many lubrication problems in highly loaded applications. It may well be that this property assists in cam/tappet lubrication, allowing ZDDP reductions but I am only guessing.

Indeed. We collected my Son's new Honda motorbike at the weekend and the Manager explained that we should use mineral oil in the sump for the first 600 miles and then drain and replace it with fully synthetic. I observed that we were doing exactly the same 40 years ago so little appears to have changed.

Richard