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01 Sep 2021

Fuelling your classic Porsche with E10 petrol

Everything you need to know about the rollout of E10 fuel

The long-planned switch to E10 fuel at the country’s petrol pumps is finally happening and it deserves your attention. While Porsche has announced the goal of going all-electric by 2030, fuel in general and E10 in particular will be a fact of life for us all in the meantime and potentially long afterwards too. In light of this, it is prudent to be aware
of the ramifications.
It may be helpful to start with the fundamentals. The default E5 fuel that has been readily available for years at just about any pump consists of up to 5% biofuel – specifically, ethanol – and the remainder is petrol. The change to E10 will see this ratio modified to up to 10% biofuel from this September onwards. While E5 will still be available in some locations as a ‘Super’ grade, E10 will become the new default option at the pump.
This change is being undertaken for environmental reasons and the Department for Transport (DfT) estimates that this relatively modest adjustment will have a vast cumulative impact on the country’s carbon dioxide (CO2 ) emissions. The intended result is cutting CO2 emissions by approximately 750,000 tonnes per year, which the DfT notes would be the equivalent of taking every car in north Yorkshire off the road permanently – although R7 may understandably find this notion uncomfortable.
Less pollution is a good thing for all of us, of course, but there are a couple of potential catches, the root causes of which are a matter of chemistry. The first catch is that E10 will be less efficient than E5, no matter what you drive. Ethanol can be an effective fuel on its own and the first ethanol-fuelled vehicle engine was patented back in 1826, but petrol became the preferred option when the internal combustion engine took off because it offers a superior power to weight ratio.
When applied to the E10 rollout, this translates to lower mileage. Burning one litre of pure ethanol gives off 34% less energy than burning the same amount of pure petrol, and increasing the amount of ethanol in our default blend of fuel will magnify this effect accordingly. The change in the level of ethanol may only be from 5% to 10% at most, but it will doubtless add up and anyone paying attention to their mileage will likely notice a statistically significant reduction.
The second catch may be the more severe one. Ethanol is a powerful solvent, so E10 can have a destructive effect on vulnerable components that potentially leads to unpleasant and expensive surprises. It has already been introduced in parts of the USA, Australia and several European countries, so we can look to their hard-won lessons to at least be aware of where the potential pitfalls can be found in advance.
The country’s car clubs have long been seriously concerned by the rollout of E10 because older engines and fuel systems that were never designed to use ethanol routinely contain materials which can react badly to it. Accelerated corrosion, rubber seals breaking down, pinhole leaks in fibreglass parts, cracking pipes and a host of other problems have all been found elsewhere in the world and the result has been no end of headaches.
Ethanol is also a hygroscopic substance – meaning it absorbs water – and water it pulls from the air in the empty parts of a tank can end up in the fuel mixture. This can translate to starting difficulties if the water content is high enough, especially in cold weather, and the engine may not run that smoothly either.
Fortunately, Porsche has prepared for this change for some time now, so not every model in the line-up will be affected and later models will be safe. Porsche Cars Great Britain advises that “E10 fuels are suitable for refuelling and thus for running all Porsche vehicles as of year of construction 1996. Specifically, the Boxster (model year 1997) and Carrera (model year 1998) models onwards. These new fuels… can be used in all new Porsche vehicles without any problems.”

Unfortunately, earlier models aren’t so lucky and many well-known parts of Porsche’s historic line-up will not be able to use E10. To find out if your Porsche is affected, a list of models that are not compatible with E10 and their years of construction has also been released by Porsche Cars Great Britain:
• 356 (1950-65)
• 911 (1965-89)
• 912 (1965-69 and 1976)
• 964 (1989-94)
• 993 (1994-98)
• 959 (1988-89)
• 914 (1970-77)
• 924 (1976-88)
• 944 (1981-91)
• 968 (1991-95)
• 928 (1977-95)
However, the rollout of E10 does not automatically spell doom for classic models and, as mentioned earlier, E5 will still be on sale for the foreseeable future. That said, exactly where it will be on sale is something of a moving target. Not every petrol station will stock it and, even among those that currently do, there will inevitably be changes over time in response to the ever-shifting tides of supply and demand. For now, making a comprehensive list of every location that won’t become rapidly outdated is impractical.
But moments like this are where clubs shine brightest and your local Region will likely be the best source for information about where E5 can still be found near you. Similarly, if you are in a position to share information of your own, your forum post could well be what saves someone else’s day. The Register for your particular model may also be a good source of advice (or, at least, friendly commiseration) if you are experiencing issues.
The switch to E10 is by no means the end of the road, but it may prompt fairly major detours in some cases. The appropriate course of action will depend on your Porsche and your location – with so many models and so many variations in what type of fuel is available where, one size cannot fit all – so exercise caution and common sense. With those and a little luck, we will all still be enjoying our Porsches for many years to come.

Stay ahead of the switch with Esso
Esso’s Synergy Supreme+ Unleaded (SU99) will remain on sale and offers a high-octane, ethanol-free alternative for those whose cars aren’t compatible with E10 fuel. It also contains detergent additives that help keep your engine clean, making it Esso’s best-ever fuel for keeping your engine in top condition. If you would like guidance on which is the right fuel for your car before filling up, you are more than welcome to check with the staff at Esso-branded service stations too.

Don’t be confused by the E5 grade label that service stations are legally obliged to carry on their pumps. The label indicates a fuel contains up to five per cent ethanol and in most parts of the country (apart from sites supplied in Devon, Cornwall, Teesside and Scotland) Esso Synergy Supreme+ 99 fuel is ethanol free.
From now until 31 December Club members using an exclusive Porsche Club branded Esso Card™ can save 6p off premium fuels (both unleaded and diesel) and 1p off standard fuels (both unleaded and diesel).
Claim your Esso Card™
The exclusive PCGB-branded Esso Card™ is available now. If you haven’t already done so, apply for yours online at or call 01270 531 992 quoting ‘Porsche’ for more details.

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