Gas and Oil Mix Ratio Calculator
How to Calculate Gas and Oil Ratios
Two-stroke (2-cycle) engines, commonly found in chainsaws, weed whackers, and outboard motors, do not have a separate oil reservoir. Instead, they require a precise mixture of gasoline and 2-cycle engine oil to lubricate the internal components while running. This Gas and Oil Ratio Calculator helps you determine exactly how much oil to add to your fuel container to achieve the manufacturer's recommended mix.
To use this calculator, simply enter the amount of gasoline you have, select your unit of measurement, and input the ratio required by your equipment. The "Ratio" refers to parts of gasoline to parts of oil (e.g., 50:1 means 50 parts gas to 1 part oil).
Common 2-Stroke Mix Ratios
Most modern small engines use one of the following standard ratios. Always check your owner's manual for the specific requirements of your equipment.
| Ratio | Oil per Gallon (US) | Oil per Liter |
|---|---|---|
| 32:1 | 4.0 fl oz | 31.25 ml |
| 40:1 | 3.2 fl oz | 25.0 ml |
| 50:1 | 2.6 fl oz | 20.0 ml |
Importance of a Correct Mixture
Getting the ratio right is critical for the lifespan of your engine:
- Too Little Oil (Lean Mix): If the ratio is too high (e.g., 100:1 instead of 50:1), the engine lacks lubrication. This causes excessive heat, friction, and can result in the piston seizing or permanent engine damage.
- Too Much Oil (Rich Mix): If the ratio is too low (e.g., 20:1 instead of 50:1), the engine will produce heavy blue smoke. This leads to carbon buildup, "fouled" spark plugs, and a clogged muffler or spark arrestor.
Example Calculation
If you have 2.5 gallons of gasoline and your chainsaw requires a 40:1 ratio, the calculation works as follows:
1. Convert gallons to fluid ounces: 2.5 × 128 = 320 fl oz.
2. Divide the total ounces by the ratio: 320 / 40 = 8.0 fl oz of oil.