Seals, plastics and metals may be damaged over longer periods of time because of bioethanol’s corrosive properties.
It may also cause some pre-detonation, or pinking, which is when the car sounds like the engine is knocking.
The car may run a little rough and may have difficulty cold starting, but it shouldn’t be a disaster for the driver.
If this does happen, the RAC advises the driver to simply top up with the correct fuel.