Mixing E0, E10 and E20: Ethanol Percentage Examples
Calculate an approximate ethanol percentage after mixing petrol blends, understand residual fuel, and keep vehicle compatibility separate from the arithmetic.
Key Takeaways for Indian Motorists:
- Adding E0 dilutes ethanol; it does not remove ethanol already present.
- The estimate needs both fuel volumes and actual blend percentages.
- The result does not calculate octane or certify compatibility.
Table of Contents
What happens to the ethanol percentage?
The Alternative Fuels Data Center describes blends using ethanol's share of the fuel. If the volumes and percentages of two fuels are known, a volume-weighted calculation gives a practical estimate of their combined ethanol share.
Estimated ethanol percentage = (litres A x percentage A + litres B x percentage B) / total litres.
This simple model assumes additive volumes and evenly mixed fuel. It is an estimate, not a laboratory measurement or a recommendation to mix incompatible fuels.
Worked examples
| Fuel already present | Fuel added | Approximate result |
|---|---|---|
| 10 litres of E20 | 10 litres of E0 | E10 |
| 5 litres of E20 | 15 litres of E0 | E5 |
| 10 litres of E10 | 10 litres of E20 | E15 |
| 5 litres of E20 | 5 litres of E20 | E20 |
For the first example, 10 litres at 20% contains about 2 litres of ethanol. Adding 10 litres with none gives about 20 litres in total, of which those 2 litres represent 10%.
Does a refill make the tank E0?
If ethanol-blended fuel remains in the tank, adding E0 does not make the entire contents ethanol-free. Even an accurately identified new purchase does not describe all the fuel already present.
Do not use a gauge estimate as if it were a measured laboratory volume. If the residual quantity or the original blend is unknown, the result must stay uncertain. An apparently precise decimal answer would hide uncertain inputs.
Does the same formula calculate octane?
This ethanol calculation does not establish the octane rating of the final fuel. Keep it out of decisions that require a confirmed octane specification. Similarly, arriving at an estimated E10 value does not prove that a vehicle is approved for the resulting fuel.
Use the compatibility checklist and the manufacturer's advice if you are unsure about a fill. Do not attempt to remove ethanol by adding water or transferring petrol into improvised containers.
How should a mixed-fuel mileage result be recorded?
Record the previous fill, the estimated residual fuel and the new purchase. Describe the result as a mixed tank rather than attributing it solely to the latest product. For a cost comparison, the fuel-cost calculator accepts your measured mileage without claiming the calculation identifies the fuel's composition.
Sources and Further Reading
Sources checked on September 7, 2026. Product information and local availability can change.
Compare Your Fuel Costs
Compare current prices using your own distance and measured mileage.
Find 0% Ethanol Petrol Near You Instantly
Download E0 Finder for Android. Real-time verified pumps, live density logs (Form-8), turn-by-turn navigation, and crowd-verified reports across 500+ Indian cities.