E85: the high-ethanol fuel blend explained
E85 is a fuel blend of up to 85% ethanol and 15% petrol, used only in flex-fuel vehicles. It usually costs less per litre than petrol, but a car burns more of it to go the same distance, so it isn't always cheaper to run.
In this entry
What E85 is
E85 is a fuel blend of up to 85% ethanol and the rest petrol, sold as its own grade where a market supports it. The name refers to the maximum ethanol share; the actual blend often varies a little by season, since more ethanol helps cold starts and pumps sometimes reduce it in winter.
It is one point on a scale of ethanol blends: E10 and E15 are low-ethanol blends usable in ordinary petrol engines, while E85 sits at the high end and needs a compatible vehicle.
E10, E15 and E85 compared
Ethanol content is the main thing that separates these blends.
Which vehicles can use it
E85's high ethanol content means it isn't safe for every engine.
A standard petrol engine is not built for E85's higher ethanol content. Using it needs a flex-fuel vehicle (FFV), which can run on any blend from straight petrol up to E85.
Price per litre isn't the whole story
Ethanol holds less energy per litre than petrol, roughly a third less. E85 is usually cheaper per litre, but a car burns noticeably more of it to travel the same distance, so the fair comparison is cost per 100 km or per 100 miles, not price per litre.
The numbers below are illustrative, using a rough real-world consumption penalty for E85. Actual figures depend on the vehicle and current local prices.
Where E85 is sold
Where E85 is sold, and how easy it is to find, varies a great deal.
How this shows up on FuelTheGuide
E85 shows up as its own grade for the countries that publish it, rather than being folded into petrol or diesel. Most countries have no E85 data at all, and we show that as a dash, never as a zero.
If you want to compare running costs rather than pump prices, use the cost-per-tank and cost-per-distance figures in the explorer instead of the raw price, for the reason explained above.
See E85 in the fuel picker →Questions and answers
Does E85 damage a regular petrol engine?
It can. Ethanol is more corrosive to some fuel system materials and burns differently, so using E85 in a car that isn't flex-fuel rated risks damage and may affect the manufacturer's warranty.
Why is E85 usually cheaper per litre than petrol?
Ethanol is generally cheaper to produce than petrol, and in many markets it is subsidised to encourage its use as a biofuel. The lower energy content per litre means the pump price needs to be noticeably lower for E85 to be competitive on a per-kilometre basis.
Is E85 better or worse for the environment?
It depends on the feedstock and how it is produced. Sugar-cane ethanol, as used in Brazil, has a much lower lifecycle carbon footprint than petrol. Corn-based ethanol, common in the US, offers a smaller benefit. Land-use change, fertiliser and transport all affect the net figure. The US DOE Alternative Fuels Data Center summarises ethanol lifecycle emissions research.
How do I know if my car is flex-fuel?
Check the owner's manual or look for a badge near the fuel filler cap — flex-fuel vehicles often have a yellow cap or an FFV badge. In the US, the fuel door usually states the compatible fuel types. The US DOE maintains a list of flex-fuel vehicle models if you want to verify a specific make and year.
Sources and further reading
- E85 (flex fuel) US Department of Energy, Alternative Fuels Data Center, afdc.energy.gov
- Ethanol fuel blends US Environmental Protection Agency, epa.gov
- Fuel prices tool and grade lists OpenVan.camp, openvan.camp/compare/fuels/prices