Yanmar Oil question

I have allways used Castrol GTD 15W-40, API CF (CD is an older spec, CF being better). I buy it from Morrisons Supermarkets as they are normally cheapest.
 
High performance oils

Synthetic motor oils are not synthetic in the sense of being a chemical other than hydrocarbons, they are artificially produced hydrocarbons in which the molecular chain length is more strictly controlled than in the distilled product. This helps to prevent burning of the shorter chains in the combustion process, or other forms of heating, thus preventing fouling. So if you could use a synthetic that had the same additives as a CD or possibly CF rated oil it might be beneficial, although expensive.

However, that isn't the whole of the story. Additives are added to oils dependent upon their intended operating temperature, the most important of which is something to control acid value. High performance oils intended for turbo-charged trucks and high performance diesel cars are far more basic (alkaline) than those intended for normally aspirated small engines such as are used as auxiliaries in sailing boats. Unfortunately, if this particular additive is not consumed chemically by high temperatures it will be abrasive and the cooler-running engines will suffer accelerated bore wear.

The answer is to use the oil specified by the engine manufacturer. Rimula X is OK but Rotella X is better. It is possible to buy API CD rated oils but many have been superseded by API CF-4. Don't be fooled into thinking that a more expensive or higher rated oil is 'better', it isn't.
 
Re: High performance oils

So are you saying I should not use the Castrol GTD? I use it because I understood it did the job well and only cost me about £11.99 for 5 litres. (might have now gone up a bit)
 
Re: High performance oils

Not knowing what your engine is I can't say for sure. GTD is an API CF which is the highest specification I would use for a yacht engine. Personally I buy decent makes of API CD from French supermarkets, where there always seems to be a good selection.
 
Re: High performance oils

I have a 1994 Yanmar 2GM20 which has done about 1300 hours. Oil would work out very expensive if I had to buy it from a French supermarket!
 
Re: High performance oils

sorry if I have confused this thread. I have the Yanmar turbo truck engine in my boat...............hence Rimula-X and or Castrol GTD. The latter in the magnatec version as, if it does what it claims, it seems perfect for a leisure marine engine!
 
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