Top three potential E10 fuel problems (and how to get around them)

E10 fuel gov advice

Wondering about the change to E10 petrol? We’ve heard a lot of questions about the new fuel standard, and what it might do to your engine. 

There are plenty of reasons to welcome E10. But there are definitely concerns for older engines in terms of E10 compatibility. We’ll cover three potential problems - and give some tips on what to do if you’re worried. 

What is E10 fuel?

E10 fuel pump

E10 is the new unleaded fuel standard. It contains 10% renewable ethanol (bioethanol) and replaces the previous E5 fuel (5% bioethanol). Basically, this new fuel contains extra bioethanol. 

Bioethanol is a renewable energy source which can be used as a fuel in vehicles - but derived from corn rather than dinosaurs. When it burns, it releases lower emission levels which is why it’s being increased in everyday fuels. 

We already know that ethanol is an excellent fuel. We sell loads of it into very high performance cars (which are tuned for ethanol). It’s particulate-free and relatively clean-burning, thanks to the amount of oxygen in the burning process. Indirectly, crops grown for bioethanol absorb CO2, helping to offset the emissions from the rest of the fuel.

Does E10 petrol pose any problems for engines?

There are three potential problems with increasing the proportion of bio-ethanol in unleaded fuel:

  1. E10 fuel compatibility with components in fuel systems
  2. Fuel flow regulation
  3. Phase separation of fuel 

We don’t just want a list of problems, though! We want to give you clear actions you can take to mitigate each one. 

  • Is E10 petrol compatible with my fuel system?
  • Problem: Ethanol should always be used in an ethanol-compliant fuel system, where the components are compatible. Ethanol can swell up certain rubbers and plastics, as well as corroding metal. It can also dissolve lubricant layers between parts, increasing wear. 

    In older cars, with rubber lines, the rubber may swell using E10 fuel. These fuel systems tend to contain rubbers, neoprenes and polyurethanes that are susceptible to swell in the presence of ethanol. They may stop doing their jobs and start to break down. 

    You’re most likely to get a problem with classic cars, pre-millenium cars, motorbikes and petrol lawnmowers (or other petrol-run maintenance equipment). 

    What to do: E5 has been blended with UK unleaded for 10 years. We don’t know, right now, if this increase to 10% will be enough ethanol to start seeing these problems but it’s best to assume so. (or could you say, but if you have any concerns then this is what you can do)

    For now, the UK government is providing an E10 compatibility checker. If you’ve got an older car, check to see if you’re on the compatible list on the E10 checker. 92% of cars are. If yours isn’t, then stick to super unleaded, which is unchanged. Super unleaded in its current form will be available for another 5 years.

  • What impact does E10 fuel have on fuel flow?
  • Problem: Because ethanol contains so much oxygen, you need to put more fuel in the cylinder for a safe air/fuel ratio (AFR). Modern cars tend to run electronic fuel injection. This provides some capability to adjust engine parameters - such as amount of fuel added and changing timing. 

    With a move to E10 in regular unleaded, newer cars will adjust fueling accordingly. Older cars, however, may not have the capability to adjust. They risk running lean - meaning there is not enough fuel flowing through. This increases engine malfunction (i.e. knock and/or engine pre-ignition). 

    What to do: If you’re concerned about performance or potential engine damage, then as above: stick with unchanged super unleaded. You can also add a high-quality octane booster such as Klotz; see below for more information. 

  • Will e10 fuel spoil faster in my petrol tank?
  • E10 petrol with additive

    Problem: This one - phase separation - is potentially our biggest concern. Ethanol is hygroscopic - meaning it absorbs moisture out of the air. Moisture bonds to the ethanol molecules, causing separation of the fuel. This means:

    • Petrol and ethanol split
    • Water and ethanol sit on the bottom of the petrol tank as a separate layer

    All of this means that fuel won’t store for as long - so it spoils more quickly. 

    What to do:  If you’re using your car infrequently, or have concerns about phase separation, then you should use a fuel stabiliser. Klotz Higher Octane Booster stabilises fuel and prevents phased separation of fuel. It also provides lubricity to the upper engine components, which can negate the effects of additional ethanol. 

    In fact, if you’re storing your motor over winter, a fuel stabiliser is essential regardless of the E10 fuel change. 

    E10, octane levels, and petrol quality

    Just a quick note. When this change happened in America, it was suspected that the non-ethanol element - the petrol it’s blended with - was of lower quality and less refined. 

    We know that bioethanol is of higher octane. However the octane numbers in the fuel weren’t changing (95 RON in the UK). 

    If ethanol is increased, the octane level needs to be brought back down to 95 RON from somewhere. We suspect this means poorer-quality petrol in the blend. 

    So - should I be concerned about E10 fuel?

    Ethanol is a fantastic fuel. The issues those with newer cars should be concerned about are around:

    • reduced quality of petrol it’s blended with 
    • the fact it will absorb more water and break down more quickly 
    • regulating the amount of fuel being used

    All these problems can be alleviated by a high-quality, all-in-one octane booster and fuel stabiliser.

    We recommend and rate Klotz Higher Octane Booster to help stabilise fuel as well as keeping it in tip-top condition. It reduces fuel-related engine knock and detonation. (and for general protection a bottle can last for 3 or 4 tanks when used sparingly)

    For the record, at Birch Performance we use Klotz HOB in all our unleaded cars, alongside super unleaded - upto and including our 1200 BHP Nissan GT-R. 

    Super unleaded isn’t changing for now, so is the best option for older cars.  If you’re in a bond and cannot get the right octane grade, then Klotz can be used in a higher dosage.

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