E10 Petrol: Which Cars Can Use It Safely?

What is the difference between unleaded and super-unleaded

The primary difference is that standard unleaded possesses 95RON and super unleaded is rated at least 97RON. Standard unleaded is also blended with up to 10% ethanol; super unleaded contains up to 5% ethanol.

What does RON mean?

RON means Research Octane Number. It is a measurement of a fuel’s ability to burn smoothly in a petrol engine without detonating. This explosion sounds similar to a metallic rattle and is also known as ‘pinking’, ‘pinging’, or ‘knock’. It may not sound severe but fuel that explodes uncontrollably, rather than burning smoothly, can cause severe engine damage, including holed pistons and pitted valves.

As it can be so harmful, modern engines possess ‘knock’ sensors that make adjustments but result in a loss of power.

Therefore, there is the potential for higher octane fuels, such as Super Unleaded, to release more power from an engine, especially if it is turbo, or supercharged.

E10 vs E5 petrol

E5 refers to petrol that contains up to 5% ethanol. E10 contains up to 10%. Some countries possess higher percentages, such as E20 (up to 20% ethanol), E85 (up to 85% ethanol) and E100 (pure ethanol).

You might think that ethanol, being a renewable fuel grown from crops, is relatively harmless. The opposite is true. While these downsides tend not to be a problem with the low concentration of ethanol used for E5, the risk of the following issues rises considerably, when the percentage of ethanol rises above 5%.

Will my fuel consumption increase, using E10 petrol rather than E5?

Like-for-like, yes. As E10 petrol contains less energy than E5 fuel of the same octane rating, fuel consumption increases by around 1-2%. This is according to the UK’s Department of Transport.

The car may also need servicing more frequently. Our other blog provides some general advice on the topic.

A justification for more frequent servicing is that more ethanol in petrol increases the deposits produced, which the oil must carry. For more advice on engine oil, consult this blog.

Does E10 petrol go off quickly?

The first problem is that, being a foodstuff, ethanol goes stale. While all petrol ages, E10 petrol deteriorates faster than either pure fossil-fuel petrol, or even E5, thanks to its elevated oxygen content.

With E10, it has been found that significant ageing can begin within two weeks of ethanol being blended with petrol at the refinery.

Just like eating food past its use-by date, expecting an engine to run on old E10 petrol has consequences. Not only will the engine produce less power but also the fuel will not burn cleanly.

This can result in deposits building within both the engine and its fuel system. These accumulations reduce efficiency and reliability but increase fuel consumption and exhaust emissions.

A further issue is that the ethanol content within the petrol absorbs moisture. Once this reaches a critical point, the water/ethanol mix drops out from the petrol.

The incombustible deposit at the bottom of the tank that results from this phase-separation can cause non-starts, or running issues. The remaining low-octane petrol above it will also ensure the engine does not run properly.

Fortunately, you can buy additives to pour into the tank that reduce the rate of ageing, if you do not tend to refuel your car at least monthly. Alternatively, you can use E5 fuel.

These tips are also useful for your gardening equipment, although many professionals prefer to use E5.

Can I put E10 petrol in any car?

No. Ethanol attacks certain rubbers and plastics and corrodes some metals such as brass, copper and aluminum. Therefore, certain cars are not compatible with E10 petrol, because the materials used within their fuel systems will be damaged by the fuel.

E10-compatible cars contain materials that can resist the ethanol within E10. As a guide, pre-2002 cars cannot use E10. Yet, some models from the 1970s can use it.

To find out, contact your car manufacturer for clarification but consider that the UK Government has published a useful online checker that is free to use: www.gov.uk/check-vehicle-e10-petrol .

Can classic cars run on E10 fuel?

According to the Department of Transport, E10 is likely to corrode carburettors, block fuel filters, damage pumps and cause further issues with flexible rubber-based fuel hoses.

It is best to check with marque specialists, or those with in-depth knowledge of specific fuel systems. Some carburettor specialists provide spare parts that are made from E10-resistant materials, such as Viton rubber.

Yet, when working on fuel systems, consider that some blends of replacement rubber fuel hose are not ethanol-resistant. These degrade quickly with E10 and even some E5 fuels, increasing the risk of fuel leaks and fires.

To be sure, ensure that all replacement rubber complies with SAE J30R9 (or ‘R9’) and is sourced from a reputable supplier. We have heard of counterfeit R9 hoses being sold on online marketplaces that are incompatible with ethanol, so be careful.

Consider also that E10 fuel causes engines to run on a comparatively weaker fuel/air mixture, compared with E5. Modern fuel injection systems compensate automatically but older cars may require manual carburettor adjustments.

This advice is also valid for garden machinery, such as petrol-powered strimmers, or chainsaws.

What happens if I accidentally fuel my car with E10?

Unlike tanking a petrol car with diesel, E10 misfuelling consequences are neither as instant, nor as severe. Therefore, it is unlikely that extra safeguards, such as misfuelling insurance cover, will be necessary.

Yet, ethanol will start attacking materials immediately. If you notice that you have used the wrong fuel, stop immediately and fill the tank with E5.

Consider also that using a fuel with the wrong octane rating can cause damage more quickly than ethanol. Should you misfuel the car, you may need to adjust the engine’s fueling and ignition settings.

What help do I need with E10 fuel?

Should your car suffer from the effects of elderly E10 fuel, by not starting, or not running properly, then GEM can help. Additionally, if you use the wrong fuel,

including that with an incompatible RON, GEM can perform the necessary adjustment to get you on your way.

Therefore, GEM echoes ADAC’s advice: only use E10 petrol on cars that are designed to use it. You can look up your car on this list to see if it is compatible:

https://check-vehicle-compatibility-e10-petrol.service.gov.uk/

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