Calculating your efficiency improvement is straightforward once you know the Fuel Efficiency Improvement formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Fuel Efficiency Improvement Calculator.
What is Fuel Efficiency Improvement?
The Fuel Efficiency Improvement calculation tells you your efficiency improvement from a few simple inputs. The figure you are solving for here is the efficiency improvement, expressed in percent.
The Fuel Efficiency Improvement formula
The core formula is:
Efficiency improvement = (New fuel efficiency - Old fuel efficiency) ÷ Old fuel efficiency × 100Here is what each input means:
- Old fuel efficiency — a value measured in km/l. Example: 12 km/l.
- New fuel efficiency — a value measured in km/l. Example: 15 km/l.
How to calculate it step by step
- Write down the old fuel efficiency (for example, 12 km/l).
- Write down the new fuel efficiency (for example, 15 km/l).
- Apply the formula above to get your efficiency improvement.
- Double-check the result with the Fuel Efficiency Improvement Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Old fuel efficiency | 12 km/l |
| New fuel efficiency | 15 km/l |
| Efficiency improvement | 25.00% |
With old fuel efficiency of 12 km/l and new fuel efficiency of 15 km/l, the efficiency improvement works out to 25.00%.
Example 2
With old fuel efficiency of 24 km/l and new fuel efficiency of 15 km/l, the efficiency improvement works out to -37.50%.
| Result | Value |
|---|---|
| Efficiency improvement | -37.50% |
Example 3
With old fuel efficiency of 6 km/l and new fuel efficiency of 15 km/l, the efficiency improvement works out to 150.00%.
| Result | Value |
|---|---|
| Efficiency improvement | 150.00% |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Fuel Efficiency Improvement Calculator does it instantly, for free, with the formula and a worked example built in.
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