The Government made adjustments to the standard grade of unleaded petrol here in the UK, and introduced this change back in 2021. Principly, it revolves around the percentage of biofuel in the blend, which was previously 5% (known as E5), but this was increased to 10% biofuel in what is known as E10.
The principle benefit to the switch was to reduce the amount of green house gases being emitted into the atmosphere, without modifications needing to be made to most vehicles. However, some vehicles will not run on E10 petrol and need to keep using E5 petrol. E5 grade petrol is now restricted to premium versions, such as Shell Vpower, BP Ultimate, or Tesco Momentum, which can be as much as 20 pence a litre more expensive than the new normal E10.
I enquired directly with Suzuki whether or not my 2006 Alto will run on E10, and they confirm that it would. However, I’ve switched back to E5 for a number of reasons.
Firstly, is fuel economy and cost. I can get up to 50 more miles out of a tank of fuel when running E5, which is usually around 330 to 350 miles to the tank if I run the car right to the top of the reserve portion of the gauge. With the new E10 grade, I barely get 300 miles out of the tank. Tesco Momentum isn’t too badly priced, but it’s very frustrating that the UK Governement has introduced a situation where I’m being ripped off whichever choice I make. Whether, I pay the premium for better quality fuel, or use E10 with a lower range, I’m loosing out regardless. That’s even before the elevated fuel prices being charged at the pumps.
Secondly, performance is far better with E5. Forgive my poor science as it’s been a while since I’ve studied the subject, but as far as I know. Biofuel has a lower octane number than fossil fuel. Essentially, there’s more engery store in fossil fuel, so you get more out of it. This is certainly noticeable, as with E5, my Suzuki Alto accelarates much faster with E5 in the tank. Therefore, running E10 means you need to burn more fuel (increasing pollution), and most likely explains the significantly lower range when running E10.
Finally, E10 is hydroscopic, meaning the fuel absorbs water. This is more of a problem if the car isn’t used very often, but water in the fuel can damage engine components and cause rusting to metal components in the fuel system. Not ideal, if like my Alto, your fuel tank is made from metal. I also understand that biofuels are harmful to some types of rubber, which isn’t great for fuel lines.
Hopefully, I’ve not baffled you with some random numbers, and the above makes sense. As much as I don’t want to give more money to the rich, fat cat fuel companies than I have to, I do think that paying the premium to stick with E5 is the better option. That being said, I don’t think there the slightest bit difference to the old normal E5 petrol and the premium branded ‘new’ E5 that I’ve felt the need to adopt.