What will be the effect of more ethanol on fuel?

Currently, most petrol sold in the UK is E5 i.e 5% ethanol. I understand that the Government is considering increasing this to 10%. What would the effect of this be, especially on older cars, and in both performance or economy and in the corrosion of engines and fuel systems?

Asked on 26 February 2020 by George Macfarlane

Answered by Keith Moody
This is a long-running issue and there's not enough hard evidence as to what the problems would be. In a nutshell, anecdotal evidence tells us that E10 can destroy rubber and fibreglass, which can obviously have a detrimental impact on older cars where these components are used. E10 is also 'less powerful' so expect to have to fine-tune your performance. There are a couple of options out there if you're concerned, involving fuel additives that might be worth looking into. Last year, the Government introduced better labelling on fuel pumps so you'll be able to see which fuel is E5 and E10.
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