2-Stroke Mixed Fuel Calculator
US Gallons
Liters
Enter the first number of your ratio (e.g., if ratio is 40:1, enter 40).
Calculation Result
Understanding Fuel Mix Ratios
A 2-stroke (or 2-cycle) engine does not have a dedicated oil reservoir like a car engine. Instead, the lubrication oil is mixed directly with the gasoline. Getting the ratio correct is vital: too little oil (lean) causes friction and engine seizure, while too much oil (rich) causes spark plug fouling and heavy smoke.
Common Ratios and Their Uses
- 25:1 – Common in older vintage engines and some high-stress heavy machinery.
- 32:1 – Frequently used in older dirt bikes and high-performance racing chainsaws.
- 40:1 – A standard ratio for modern chainsaws, leaf blowers, and string trimmers.
- 50:1 – The most common ratio for modern handheld power equipment and outboard motors.
How to Calculate Manually
To find the amount of oil needed, you divide the total amount of fuel by the ratio number. For example, if you have 128 ounces of gas (1 gallon) and need a 50:1 mix:
128 / 50 = 2.56 Fluid Ounces of Oil
Practical Examples
| Gas Amount | Ratio | Oil Needed |
|---|---|---|
| 1 Gallon | 50:1 | 2.6 fl. oz. |
| 1 Gallon | 40:1 | 3.2 fl. oz. |
| 5 Liters | 50:1 | 100 ml |
| 5 Liters | 25:1 | 200 ml |