If you own a chainsaw, leaf blower, or string trimmer, you've likely seen the "50:1" requirement printed on the gas cap. This ratio is critical for 2-stroke engines, which do not have an independent oiling system. Instead, the lubrication for the piston and crankshaft is provided by the oil mixed directly into the gasoline.
What Does 50:1 Actually Mean?
A 50:1 ratio means that for every 50 parts of gasoline, you need 1 part of 2-cycle engine oil. Using this specific ratio ensures that the engine stays lubricated without creating excessive smoke or "fouling" the spark plug with unburnt oil residue.
Standard Mixing Ratios Reference Table
Gasoline (Gallons)
40:1 Ratio (Oil Oz)
50:1 Ratio (Oil Oz)
1 Gallon
3.2 fl oz
2.6 fl oz
2 Gallons
6.4 fl oz
5.2 fl oz
5 Gallons
16.0 fl oz
12.8 fl oz
How to Mix Your Fuel Safely
Use Fresh Fuel: Always use gasoline with an octane rating of 89 or higher. Avoid ethanol-blended fuel (E15 or E85) as it can damage small engines.
Use Quality 2-Stroke Oil: Ensure the oil is rated for air-cooled engines (ISO-L-EGD or JASO FD).
The "Oil First" Rule: Pour the oil into a clean, approved gas can first, then add the gasoline. This helps the liquids mix thoroughly.
Agitate: Close the gas can tightly and shake it gently before fueling your equipment.
Common Mistakes to Avoid
The most common mistake is assuming "more oil is better." While running a slightly "rich" mix (like 40:1 in a 50:1 machine) might cause some extra smoke, running a "lean" mix (too little oil) can cause the engine to overheat and seize, resulting in permanent damage. Always stick as close to the manufacturer's recommendation as possible using our 50 to 1 gas mix calculator.
function calculateGasMix() {
var gasAmount = document.getElementById("gasAmount").value;
var unitType = document.getElementById("unitType").value;
var ratio = document.getElementById("ratioValue").value;
var resultDiv = document.getElementById("resultBox");
var oilOutput = document.getElementById("oilResult");
var summaryText = document.getElementById("mixSummary");
if (gasAmount === "" || gasAmount <= 0 || ratio <= 0) {
alert("Please enter valid positive numbers for both gas amount and ratio.");
return;
}
gasAmount = parseFloat(gasAmount);
ratio = parseFloat(ratio);
var oilAmount = 0;
var resultString = "";
if (unitType === "gallons") {
// 1 US Gallon = 128 fluid ounces
var totalOuncesGas = gasAmount * 128;
oilAmount = totalOuncesGas / ratio;
resultString = oilAmount.toFixed(2) + " Fluid Ounces (fl oz)";
summaryText.innerHTML = "To get a " + ratio + ":1 ratio with " + gasAmount + " gallons of gas, add " + oilAmount.toFixed(2) + " oz of 2-cycle oil.";
} else {
// 1 Liter = 1000 milliliters
var totalMlGas = gasAmount * 1000;
oilAmount = totalMlGas / ratio;
resultString = oilAmount.toFixed(1) + " Milliliters (ml)";
summaryText.innerHTML = "To get a " + ratio + ":1 ratio with " + gasAmount + " liters of gas, add " + oilAmount.toFixed(1) + " ml of 2-cycle oil.";
}
oilOutput.innerHTML = resultString;
resultDiv.style.display = "block";
}