Should I always keep my car full of fuel?

I have owned a new Toyota C-HR PHEV for a year and apart from the occasional very long journey realise that filling up with petrol is not a frequent requirement as many local journeys can be managed on the 42 mile battery range or might only need a few miles with the IC engine, even though I live in a rural area. Conscious that today's fuels can go "stale" or degrade with time, what advice can you offer as to how full I should keep the tank and if there are some grades of fuel better than others for this type of motoring. In the past with purely petrol cars I have always tended to keep the tank fairly full in case I need to go somewhere at short notice. Even though I know I am carrying around a weight penalty of extra fuel. It's probably a psychological thing!

Asked on 5 July 2025 by Chris Willsher

Answered by David Ross

E10 fuel, now the standard for regular 95RON unleaded in the UK, does indeed go 'off' sooner than E5. In a sealed container, it should last 3-6 months, with factors including ambient temperature having an effect on exactly how long it is. There isn't any clear, consistent guidance on how long it should last within a fuel tank, but if you're filling very infrequently, it'd be sensible to consider only using super unleaded, which is still E5. As for how full to keep it, we'd suggest somewhere from a quarter to a half full.

Tags: petrol phev fuel level

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