Fuel Octane Ratings Guide
Car drivers now have more choice than ever on the fuel types available in service stations today. Unleaded, Super Unleaded, Bio Diesel and Diesel to name a few. On the petrol service station pump you may see a RON octane rating typically RON 95 on unleaded and RON 97 or 98 on super unleaded petrol.
What do the octane numbers mean?
The Research Octane Number (RON) is commonly found on petrol pumps in service stations throughout the UK. Octane ratings are a measure of a fuels ability to resist engine knocking (pinking or pinging) which we discuss next. Motor Octane Number (MON) is another measure which tests fuel for knock resistance under more vigorous conditions by higher engine speed, variable engine timing and a preheated fuel mixture.
What is engine knocking?
The fuel and air mixture in the cylinder should be ignited by the spark plug and burnt in one smooth explosion. When knocking occurs, additional explosions take place by unburnt pockets of fuel and air mixture during the downward stroke of the piston away from the top of the cylinder bore. Engine knocking can also be referred to as pinking or pinging.
Do higher octane levels increase performance?
This is a common misconception. Using fuel with a higher octane level than recommended for your car will only hinder performance. Given that higher octane fuel is more expensive, you will only be reducing the fuel economy and performance of your car and paying for the privilege. You may even damage the engine.
For the best performance and fuel economy, check your car owners manual for recommended fuel and stick with it. This together with regular servicing is the best way to ensure you are getting the most MPG out of your car.
Summary
In this article I decided not to include details about the chemical structure of fuel for RON and MON testing. On doing my research for this article I found some very interesting websites which go into great detail on the chemicals of fuel which I did not feel was neccassary for this article.
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