# E10 or E5? What to Leave in the Tank of a Laid-Up Lotus This Winter

Ethanol in petrol absorbs moisture and can attack old fuel hoses. What the official advice says, and which grade to fill a Lotus with before winter.

Source: https://lotustrails.com/blog/2026-11-05-e10-petrol-and-winter-storage/

The last of the good autumn weekends are going, and a lot of Lotuses will make one final trip to the filling station before they are put away. Which pump you use on that trip matters more than it does the rest of the year.

## What changed at the pump

Standard 95 octane petrol became E10, meaning up to 10 per cent ethanol, in Great Britain in September 2021 and in Northern Ireland in November 2022. The super grade, 97 octane and above, is still E5 at most filling stations that sell two grades. The government says some small or rural stations may sell only one.

According to GOV.UK, most petrol cars on the road can use E10. The exceptions it names are "classic, cherished and older vehicles" and some models from the early 2000s. Its advice for anyone unsure is simple: keep using E5.

## Where older Lotuses stand

This is where it gets awkward for owners of K-series cars such as the [Elise S1](/models/elise-s1/), the [Exige S1](/models/exige-s1/) and the [340R](/models/340r/). The government's online checker relies on information from manufacturers and does not cover every make, and Lotus's own fuel guidance page does not say which older models are cleared for E10. Without a clear yes from the maker, the official fallback is E5.

Earlier cars are another step back. Lotus Marques, a specialist in older Lotuses, recommends ordinary petrol without ethanol for the twin cam engine in cars such as the Elan, and suggests replacing rubber fuel hoses about every ten years whatever fuel is used.

## Why winter storage makes it worse

Using E10 now and again is less of a worry than leaving it to sit. GOV.UK says a single tank of E10 in a car that is not compatible "should not be a major problem", but that prolonged use may cause harm.

The Federation of British Historic Vehicle Clubs (FBHVC) gives more specific advice for storage. For a vehicle laid up for a long period, it recommends replacing E10 with ethanol-free petrol. It also advises against draining the fuel system completely, because a dry system can corrode and its seals can be damaged. It says it knows of no additive that fully protects rubber and gasket materials from E10, though it does recommend a corrosion inhibitor in both E5 and E10.

## What to do before the car goes away

- **Fill up with super grade E5 on the last drive.** Some super E5 fuels contain no ethanol at all, according to the FBHVC, but this varies by brand and area.
- **Leave the tank full rather than empty.** That follows the FBHVC's warning about dry systems.
- **Look at the fuel hoses.** If they are old, cracked or of unknown age, have them replaced with ethanol-resistant hose before spring.
- **Check the handbook or ask a specialist** if you are not sure what your car can use.

For the checks to do before the first trip next year, see the [road trip preparation guide](/guides/road-trip-preparation/).

Sources: [GOV.UK, E10 petrol explained](https://www.gov.uk/guidance/e10-petrol-explained); [FBHVC, clarification on E10 fuel usage for historic vehicles](https://fbhvc.co.uk/news/article/fbhvc-clarification-on-e10-fuel-usage-and-labelling-for-historic-vehicles); [Lotus Marques, fuel hose compatibility with ethanol blended fuels](https://lotusmarques.com/info/knowledge-base/1094-fuel-hose-compatibility-with-ethanol-blended-fuels).