Engine Oil API classification

S

srah1953

Well-Known Member
Joined
21 Jun 2007
Messages
493
Location
Ireland, Carlingford
Visit site
Hi All
According to the Yanmar manual, the engine oil should be 15W40 or 10W30 with an API classification of CF-4 or CI-4. Looking in Halfords, all the oils had on them “meets API CF classification” without any reference to a number. Does this matter?
Thank you
 
Yes, the TBN of CF is a good deal higher than CF-4. Better to find the correct grade. Personally I see little point in using 10W/30, bearing life will be better with the heavier grade. Which engine is this for?

More info on oils on my website under 'Engine'.
 
vyv_cox said:
Yes, the TBN of CF is a good deal higher than CF-4. Better to find the correct grade. Personally I see little point in using 10W/30, bearing life will be better with the heavier grade. Which engine is this for?

More info on oils on my website under 'Engine'.
Click to expand...

Is a higher TBN a bad thing then?:

TBN oil analysis

Oils are continually exposed to acidic compounds which cause the oil to turn more acidic. This is particularly true of crankcase oils. In an attempt to combat this problem, manufacturers give the oil a 'reserve alkalinity' which is designed to 'cancel out' any acidity which forms in the oil during use. The TBN determines how effective the battle will be against any acids formed during the combustion process. A higher TBN means the oil has more reserve alkalinity available which can be used to reduce the corrosive effects of acids.

A low TBN can also reduce the detergency of an oil and can therefore lead to fouling within the crankcase.

As a general rule of thumb, if the TBN is measured at 2.0mg KOH g-1 or less, or if it's 50% of the virgin oil TBN, the oil is considered unfit for engine protection and there is a risk that corrosion could take place. The use of a high sulphur fuel will decrease the TBN at a faster rate due to the increased formation of sulphuric acid
 
****, I just bought 8 litres of Mobile CF oil thinking it must be better than the Halford Mineral Diesel Oil, CF-4, I have been using.

Both are listed in Viv Cox's site as replacements for CD.

But you're saying we shouldn't use CF, is that right Viv?

Do you think Halford Mineral Diesel Oil, CF-4, is a good choice from among what is available here? I thought a name branded oil ought to be better quality.
 
vyv_cox said:
Yes, the TBN of CF is a good deal higher than CF-4. Better to find the correct grade. Personally I see little point in using 10W/30, bearing life will be better with the heavier grade. Which engine is this for?

More info on oils on my website under 'Engine'.
Click to expand...

Hi Vyv

The engine is a Yanmar 3JH5CE (39hp). The manual doesn't make any recommendations between mineral, synthetic or semi-synthetic. Any thoughts?

Thanks
 
The advice I have been given is that excessively high TBN can cause cylinder bore wear. Older engines generally required API CD, which has a TBN of 4. Cold running engines such as yacht auxiliaries, especially on current low sulphur fuels, cannot generate the acids to neutralise higher TBN oils.

Beware reading internet stuff on this subject, they universally refer to automotive experience in which speeds, temperatures, oil drain intervals, power, etc increase consistently. Oils develop in tandem, so synthetics and semi-synthetics have emerged. Yacht engine use, in most cases, has not changed in many years.

API CD is now nearly unobtainable in UK, although I still buy it in France and Italy. CF-4 seems to be the best alternative. Later engines such as Yanmar YM and JH have now revised their oil requirements to current production grades but my GM, only 10 years old, specified CD although it was officially obsolete years ago.

Halfords don't make oil, they will buy good stuff from a reliable distiller plus a commercial additive package. I have no problems with it and would buy it.

There is lots more about this on my website.
 
Look to Agricultural Engineers for CF-4 oils. That's where I got my last lot. Sadly the guy's retired/gone out of bussiness/moved (god knows where) so back to cheapest muck available from Auto-factors for me this year.
 
I've been using Tesco mineral diesel oil for the last few years. The 4 litre pack being about right for my Perama M25. I think it cost about £10.99 last year. This year a tad under £15!! Litre for litre Halfords Enhanced Mineral Oil is now cheaper - but what does 'enhanced' mean? Wanting to avoid nasty additives I've stuck to Tesco this time. Am I being over cautious?

The spec recommended for the Perama is CC or CD but the only thing I've found near this is a Morris's CC designed for canal boats.
 
rjp said:
The spec recommended for the Perama is CC or CD but the only thing I've found near this is a Morris's CC designed for canal boats.
Click to expand...

I am told they sell a great deal of their CC for this purpose. Many canal boats have BMC diesel engines as used in taxis, same as I have in my motorsailer, so I shall be buying it. A nice simple lubricant for simple old engines.
 
You must log in or register to reply here.

Share this page

Top