• Double-D Tyreright

What Different Fuels Mean for Your Car and its Fuel Efficiency


We mostly make posts about car, van and semi trailer tyres. But today we have a more general motoring post about fuel. We hope it helps you understand the different types or grades of fuel better.

It’s something that most of us put into our cars every day, we wouldn’t get very far if we didn’t buy it, but there are a lot of misunderstandings about different fuel types and the effect that these different fuel types might have on fuel efficiency. It might seem simple - the more expensive the fuel the better it is - but is this really the case? In this article we wanted to discuss some of the different factors to consider in different fuel types.

What does the Octane Rating mean? If you go to a Petrol Station you’ll see different fuels with different ratings - often 91,95 and 98. It’s commonly thought - the higher the Octane the better the fuel. People will pay more money for a higher octane fuel without actually understanding what effect a higher octane fuel has on their engine. It’s not really that simple.

Octane refers to the likelihood of fuel igniting under pressure - fuel igniting before the spark plugs require it to. If you have a high performance car you should buy high octane fuel for the safety of your vehicle. It may actually be a similar performing fuel with no actual increase in efficiency. Whilst a newer high performance vehicle might perform slightly better with a higher octane fuel the problem is that there is generally a fair price difference between the octane values - the higher the octane the more expensive the petrol and sometimes by a long way. The increased “efficiency” may not be worth the extra cost.

The Knock problem - This is not a problem for every car but it is a potential problem that you should pay attention to. A higher octane fuel will help to prevent the scenario called knock. Let me first explain what we mean by “knock.”

Generally an engine has the fuel sprayed into the engine and ignited only when the spark plugs light up. A pre-ignition or Knock is when the fuel ignites even before the spark plugs light up. This can cause damage and wear within the engine. Knock also means that the engine will be performing inefficiently. In most newer engines that are designed today a lower compression ratio and the computer system within the engine prevents this phenomenon from happening. With some cars however a certain octane value is required for the engine computer to work successfully. If your vehicle manufacturer recommends a certain octane fuel one of the main reasons for this may be to avoid knock.

If a modern engine has been programmed for a certain compression ratio and requires a fuel of a 91 octane or higher it's very important that it receives this type of fuel or the chance for knock will increase which can lead to extra maintenance costs.


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