Blog: Using ‘Super fuel’ – miles of smiles or burning money?

Do higher-grade 'super fuels' make a difference to way an engine runs?

Do higher-grade 'super fuels' make a difference to way an engine runs? - Credit: PA

Do higher grade 'super fuels' really make a difference to the way your car runs, Motoring editor Andy Russell looks at some of the arguments.

I'm often asked whether there are any benefits to using the higher grades of fuel, both petrol and diesel, available at many filling station forecourts.

I can't speak from any scientific point of view, but I prefer to use these 'super fuels' which, now prices have come down, are only a few pence more than standard fuel.

I can't prove the performance is better in my family car – many high-performance sports models need higher octane petrol to unleash more horsepower – or motorcycle but I feel they run better and economy is slightly improved.

It could just be the placebo effect in that if you expect it to make a improvement you swear it does.

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But I got a couple of miles per gallon more running a supermini on super unleaded petrol, and it seemed more responsive.

My wife has noticed a similar effect running her estate car on premium diesel while her business partner noticed his trip computer range rising from around 670 miles on a full tank to more than 700 miles on the better diesel.

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Most fuel brands offer higher grade fuel which is claimed, with regular use, improve performance and economy while helping to protect the engine.

Super unleaded petrol has a research octane number (RON) of around 98 compared to the standard 95 RON. Higher-octane petrol should burn more efficiently, delivering more power for less fuel burned. It particularly suits high-performance engines where pressures and temperatures are greater.

Cetane is to diesel what octane is to petrol. The cetane number is a measure of diesel's ignition delay so the higher the number the shorter the ignition delay so performance should be better.

Higher grade fuels also have extra additives to help keep the engine clean to maintain engine performance.

AA spokesman Chris Patience said: 'European fuel specifications are agreed jointly between the car industry and fuel industry to ensure that forecourt fuels are suitable for the range of engine technologies in service. So, generally, any fuel is good enough but some may be better than others and some drivers may choose to spend more on what they perceive to be a premium product. I guess it's the same thinking that results in us choosing to shop in different supermarkets.

'Few cars actually need the higher octane of premium fuel – the vehicle handbook will say if you have to use it.

'They do tend to contain more, or more effective, additives to keep the engine clean so there can be a benefit from using them every three or four tanks full, particularly if you're planning to keep the car for many years.

'Re MPG and performance, different models can be expected to respond to these fuels in different ways – try one for a couple of fills and record your fuel economy. Ultimately, it's the driver who must decide whether the additional cost is justified in terms of measured fuel economy benefit or any perceived improvement in performance and driveability.

'You have to be really careful comparing fuel consumption over a short period as it is affected by load, road conditions, weather, driving style and so on.

'There's also a risk that if you're trying something new that you expect to give you better economy you might well adapt your driving style and actually drive more economically without being aware of it. It's a challenge to eliminate all other variables and attribute a change to fuel alone,' he said.

I'd like to hear your experiences of using higher-grade, more expensive fuel. Did you get more MPG and was it worth the extra cost or did you see no difference. Email

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