Two-stroke engines (found in chainsaws, weed whackers, and older outboard motors) do not have a dedicated oil reservoir like a car. Instead, the lubricating oil must be pre-mixed directly into the gasoline. Getting the ratio correct is critical for the health of your engine.
Too Little Oil (Lean): High friction, overheating, and potential engine seizure.
Too Much Oil (Rich): Heavy smoke, spark plug fouling, and carbon buildup in the exhaust.
Common Mix Ratios Table
Ratio
Oil per 1 Gallon (US)
Oil per 5 Liters
25:1
5.12 fl oz
200 ml
32:1
4.0 fl oz
156 ml
40:1
3.2 fl oz
125 ml
50:1
2.6 fl oz
100 ml
How to Mix Correctly
1. Always use a clean fuel container specifically for mixed gas.
2. Pour half of the gasoline into the container first.
3. Add the exact amount of two-cycle engine oil calculated above.
4. Add the remaining gasoline to help agitate the mixture.
5. Close the container tightly and shake gently to ensure a thorough mix.
function updateLabels() {
var unit = document.getElementById('fuelUnit').value;
var fuelLabel = document.getElementById('fuelLabel');
if (unit === 'liters') {
fuelLabel.innerText = 'Total Gasoline Amount (Liters)';
} else {
fuelLabel.innerText = 'Total Gasoline Amount (Gallons)';
}
}
function calculateTwoStrokeMix() {
var fuelAmount = parseFloat(document.getElementById('fuelQuantity').value);
var ratioValue = parseFloat(document.getElementById('mixRatio').value);
var unitType = document.getElementById('fuelUnit').value;
var resultDiv = document.getElementById('resultDisplay');
var oilResult = document.getElementById('oilResult');
var mixSummary = document.getElementById('mixSummary');
if (isNaN(fuelAmount) || fuelAmount <= 0 || isNaN(ratioValue) || ratioValue <= 0) {
alert("Please enter valid positive numbers for both fuel amount and ratio.");
return;
}
var oilAmount;
var unitLabel;
var summaryText;
if (unitType === 'liters') {
// Calculation: (Liters / Ratio) * 1000 to get Milliliters
oilAmount = (fuelAmount / ratioValue) * 1000;
oilResult.innerText = oilAmount.toFixed(2) + " ml";
summaryText = "Mix " + oilAmount.toFixed(2) + " ml of oil with " + fuelAmount + " liters of gas for a " + ratioValue + ":1 ratio.";
} else {
// Calculation: (Gallons / Ratio) * 128 to get Fluid Ounces
oilAmount = (fuelAmount / ratioValue) * 128;
oilResult.innerText = oilAmount.toFixed(2) + " fl oz";
summaryText = "Mix " + oilAmount.toFixed(2) + " fl oz of oil with " + fuelAmount + " gallons of gas for a " + ratioValue + ":1 ratio.";
}
mixSummary.innerText = summaryText;
resultDiv.style.display = 'block';
}