Probably not a current problem, but be aware that there are plans to increase the percentage of ethanol in road fuel from 5% to 10%.

There have also been reports that E10 is a less stable fuel and that this can make it more difficult to start a vehicle that has not been driven for an extended period.

https://www.rac.co.uk/drive/advice/emissions/what-is-e10-fuel-and-how-could-it-affect-you/

I'd be more worried about running it for ten minutes. I wouldn't have thought that's long enough to evaporate the condensate it's creating that'll remain in the engine. It's certainly not long enough to warm the exhaust, that will gradually collect more and more water.

Because I've been advised to isolate for twelve weeks, I'll be keeping an eye on the battery and probably putting it on charge now and then. I'll roll the car to a different position to prevent the tyres flat spotting. I'm considering SORN and jacking it up with the tyres off the ground.

Petrol is a mixture of organic chemicals, mostly saturated hydrocarbons, with small amounts of additives to improve combustion, plus a few percent of ethanol. These components will have different volatilities, so some will tend to escape faster than others. In a closed tank the mixture will not change noticeably over weeks or months, and in the dark there will be no chemical change either. Petrol would be a much more hazardous material to store if it was liable to spontaneous deterioration.

The only concession I make to fuel 'going off' is to empty the tank on my mower at the start of the winter lay-off - tho that is getting shorter each year ....

What happens when petrol is stored in a container open to the atmosphere, like a vehicle fuel tank, is that gradually the higher fraction aromatics evaporate, and at the same time if the fuel contains ethanol some water vapour will be attracted to the ethanol in the fuel.

I have found that petrol stored in a sealed container in a cool place does not seem to suffer deterioration as I store 30 to 40 litres for my standby generator in sealed plastic fuel cans. This fuel is rotated round and replaced, used in the mowers etc so is not stored indefinitely.

I dont agree with the consensus running the engine for 10 minutes in the current circumstances is a bad idea in modern cars. In fact, many UK journeys are probably not much longer than 10 minutes. Neither is doing this once a week or maybe every other week for the next 3 to 6 months suddenly going to wreck an engine or make an exhaust rust through.

In any event, if the engine has got up to temp, it wont be causing condensation.

Edited by glidermania on 04/04/2020 at 13:35