15/40 engine oil

[vyv_cox]

Apologies if I've misread the comments above. I appreciate that CD spec oil is designed with TBN of around 4, but from what I can understand, TBN is the ability to neutralise the acid byproducts. Could someone explain why a high TBN would harm a low power Marine engine ( say Bukh 20).

Thanks

Chris

Optimum wear rate is achieved when the oil is neutral. Running an engine with either acidic or basic chemistry will lead to higher wear rates. We avoid high acidity by regular oil changes. We can't avoid high alkalinity if we use oils with high TBN. There is a good deal of evidence that high TBN will lead to bore wear, perhaps cam and follower wear in the medium term. This would be bore polishing, not glazing, giving smooth, reflective surfaces that cannot transfer oil beneath the rings.

 

[lw395]

Optimum wear rate is achieved when the oil is neutral. Running an engine with either acidic or basic chemistry will lead to higher wear rates. We avoid high acidity by regular oil changes. We can't avoid high alkalinity if we use oils with high TBN. There is a good deal of evidence that high TBN will lead to bore wear, perhaps cam and follower wear in the medium term. This would be bore polishing, not glazing, giving smooth, reflective surfaces that cannot transfer oil beneath the rings.

I thought, perhaps wrongly, that high TBN oils acted like a 'buffer solution' able to absorb a lot of acid without being very alkaline? Are you really saying that all high TBN oils have a high pH? How high? (I'm guessing there has to be water in the mix to make pH a valid concept?)

'Suitable for Older Engines' = 'made from oil that's been discarded once already'? i.e. suitably cheap for engines that aren't worth buying Castrol (or your favourite make) for, rather than optimised to keep museum pieces working forever?

 

[vyv_cox]

I thought, perhaps wrongly, that high TBN oils acted like a 'buffer solution' able to absorb a lot of acid without being very alkaline? Are you really saying that all high TBN oils have a high pH? How high? (I'm guessing there has to be water in the mix to make pH a valid concept?)

'Suitable for Older Engines' = 'made from oil that's been discarded once already'? i.e. suitably cheap for engines that aren't worth buying Castrol (or your favourite make) for, rather than optimised to keep museum pieces working forever?

No, it's far more clever than that. If the oil was simply given high alkalinity it would become acidic within a very short operating time, especially with higher sulphur fuels such as red diesel. The chemicals used have the property that as they react with the acidic compounds resulting from combustion, their reaction products are in turn alkaline. In this way a modern oil can remain pretty much neutral throughout its life, which is being extended continuously to meet marketplace requirements. 12000 miles/two years is now quite common (cars, not yachts!). There should be virtually no water in lub oils, well under 0.5% and probably zero at running temperature.

'Suitable for Older Engines' usually means that the additive package is less expensive. Most oil companies' top grades are the result of huge research investments, thus they are expensive and closely guarded. Packages for lower grades such as API CD, CF, etc can be bought from a number of additive suppliers at considerably lower cost. More information on my website.

Recycling of oil is widely carried out but the result is usually an acceptable base oil, to which additives can be added. Again, these products are unlikely to be top level but probably perfectly OK for general use. I have no experience of these but understand them to be virtually indistinguishable from those of the majors.

 

[lw395]

No, it's far more clever than that. If the oil was simply given high alkalinity it would become acidic within a very short operating time, especially with higher sulphur fuels such as red diesel. The chemicals used have the property that as they react with the acidic compounds resulting from combustion, their reaction products are in turn alkaline. In this way a modern oil can remain pretty much neutral throughout its life,

We can't avoid high alkalinity if we use oils with high TBN.

Vyv, your two statements appear to contradict each other?

 

[vyv_cox]

Yes, I could have explained better. The first statement was a response to your question. TBN is not simply a matter of pouring in more KOH, it's an ongoing reaction triggered by the acids being generated.

High TBN oils are designed to neutralise more acidic conditions, induced by higher temperatures, speeds, etc. In our engines these conditions are never met, so the alkalinity is never reduced sufficiently.

Oils used as the cylinder lubricants in marine engines burning residual fuels are extremely basic, TBNs as high as 100 may be specified. Despite that the levels of sulphur present result in a near-neutral chemistry in the bores, although it may take fine tuning to get it right.

 

[lw395]

Thanks Vyv!

 

[oldgit]

Shell oil any good

£20.00 for 20L

http://cgi.ebay.co.uk/SHELL-RIMULA-...Air_Tools_and_Compressors?hash=item35a78999ec

 

[capsco]

So Fred, according to the wording in your link, instead of clicking buy now some clown has bid the price up, have I read it right?

 

[Topcat47]

This ought to have a permanant place on the PBO site, so often are questions asked about it.

 

[MinorSwing]

Does anyone know where I can buy 15W/40 API CC oil from?

 

[sailorman]

Morris oils
or do a forum search

 

[ghostlymoron]

Morris Oils only sell large quantities from their depot in Shrewsbury. You'll have to ring them to find a local stockist.

 

[theoldsalt]

Does anyone know where I can buy 15W/40 API CC oil from?

Is 15w/40 absolutely necessary?

Not 15w/40 but 20w/50. It's good for old engines and is API CC.

It's cheap and readily available (collect from local B&Q store). I have used it for years in my old Thornycroft T80.

http://www.diy.com/departments/carlube-daytona-20w50-type-engine-oil-45l/259321_BQ.prd

 

[vyv_cox]

Morris Oils only sell large quantities from their depot in Shrewsbury. You'll have to ring them to find a local stockist.

Mine was delivered to my door, 25 litre drum. I think the delivery price was included in the quote.

 

[ianj99]

All this oil type discussion is largely irrelevant imho. Just use decent quality diesel oil and more importantly: CHANGE IT EVERY SEASON.

This is far more important than dithering over which brand to buy. Unless someone can come up with conclusive proof that their marine engine has suffered because the 'wrong' oil was used in it, then there is no point, other than personal preference, in recommending make X over make Y etc.

 

[sailorman]

All this oil type discussion is largely irrelevant imho. Just use decent quality diesel oil and more importantly: CHANGE IT EVERY SEASON.

This is far more important than dithering over which brand to buy. Unless someone can come up with conclusive proof that their marine engine has suffered because the 'wrong' oil was used in it, then there is no point, other than personal preference, in recommending make X over make Y etc.

It will morph into white diesel & bio soon

 

[vyv_cox]

All this oil type discussion is largely irrelevant imho. Just use decent quality diesel oil and more importantly: CHANGE IT EVERY SEASON.

This is far more important than dithering over which brand to buy. Unless someone can come up with conclusive proof that their marine engine has suffered because the 'wrong' oil was used in it, then there is no point, other than personal preference, in recommending make X over make Y etc.

There is loads of evidence. Read any Classic car forum, for example. There is a good case history on my website from a regular contributor here. I was initially advised about problems of high bore wear in yacht engines running on high spec oil by the engine shop at Dickies of Bangor. An oil-formulator colleague at Shell confirmed the problem and offered a reason, also on the website.

 

[ianj99]

There is loads of evidence. Read any Classic car forum, for example. There is a good case history on my website from a regular contributor here. I was initially advised about problems of high bore wear in yacht engines running on high spec oil by the engine shop at Dickies of Bangor. An oil-formulator colleague at Shell confirmed the problem and offered a reason, also on the website.

Car forums are not relevant - read your own reply in post 10 and anecdotal at best. (you never get the full story behind problems).

I use ZX1 from teamzx.co.uk as a friction eliminator and anti wear additive. It has a Nato stock number so not snake oil.

If a significant number of forumites say they've suffered problems from grade/brand X oil, then I'll accept your comment. Otherwise its more down to maintenance or lack of, mistreatment, bad installation etc. (engine inclined too steeply, oil cooler fitted when not needed, engine not run at or allowed to reach operating temperature)

 

[vyv_cox]

Not sure where 'snake oil' comes into it. The problem that I am aware of relates to the use of high TBN, high performance synthetic or semi-synthetic oils in low output, cool running yacht engines, especially raw-water cooled ones. I have never discussed brands other than to say what I use.

 

[theoldsalt]

All this oil type discussion is largely irrelevant imho. Just use decent quality diesel oil and more importantly: CHANGE IT EVERY SEASON.

This is far more important than dithering over which brand to buy. Unless someone can come up with conclusive proof that their marine engine has suffered because the 'wrong' oil was used in it, then there is no point, other than personal preference, in recommending make X over make Y etc.

I think the point being made is not about the make but the specification and particularly API CC or similar (which is suitable for older engines) and where it can be purchased.