Cheap Supermark Disel

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Re: Cheap Supermark Disel

Post by CitroJim »

Peter.N. wrote:My wife's uncle use to work on the Shell ocean tankers, he said the all the fuel came from the same place.
It does. Out of the ground. But seriously yes, I believe the only divergence between say, Smell and Tesburys Value 95 RON stuff is the additives, the base fuel indeed being identical.

Indeed Mike, you are correct in that all fuel must conform to a minimum standard. It's said that whilst Morrida's Supermarket just meets the standards the stuff from say, ASSO exceeds it by a considerable margin.

Also, Octane values are another point of interest. RON is Research Octane which is defined by a different test to that of MON (Motor Octane) RON is not representative of the real world whereas the way MON is determined is. In some fuels there can be may points difference between MON and RON. For instance a fuel may be 95 RON but only 86 MON and as it hits 95 RON it's good and meets specs. but in your engine it'll behave more like an 86 Octane fuel and the ignition will retard as a consequence and performance will suffer as a result. Fuel in the UK is rated and defined by its RON value and not the more accurate MON value.

A good fuel will achieve a similar MON and RON value on test and this will behave appropriately in an engine in the real world.

The Yanks I believe rate their fuel by PON (Pump Octane Number) which is half the value of MON+RON and gives a very good real world value. the difference between the MON and RON of a fuel is known as its sensitivity.

So you can now see how a fuel with a high sensitivity will behave far worse than a fuel with a low sensitivity and this may be the difference between supermarket and the traditional purveyors of fuel. Fuel with a low sensitivity is more expensive to produce as it needs higher quality additives.

So there may be something in the belief that some supermarket fuel is not so good,

This only applied to petrol. Diesel is an entirely different kettle of fish and I'm not going into why some diesels seem better than others and the wonderful con-trick I believe premium diesel to be!