Two Stroke Oil Calculator

Two-Stroke Oil Mix Calculator

Oil to Add:

function calculateTwoStrokeMix() { var fuel = parseFloat(document.getElementById('fuelAmount').value); var unit = document.getElementById('fuelUnit').value; var ratio = parseFloat(document.getElementById('mixRatio').value); var resultArea = document.getElementById('resultDisplay'); var oilResult = document.getElementById('oilVolumeResult'); var summary = document.getElementById('mixSummary'); if (isNaN(fuel) || fuel <= 0 || isNaN(ratio) || ratio <= 0) { alert("Please enter valid positive numbers for fuel volume and ratio."); return; } var oilAmount; var resultUnit; if (unit === 'liters') { // Calculation: (Liters / Ratio) * 1000 = Milliliters oilAmount = (fuel / ratio) * 1000; resultUnit = "ml (Milliliters)"; oilResult.innerHTML = oilAmount.toFixed(2) + " " + resultUnit; } else { // Calculation: (Gallons / Ratio) * 128 = Fluid Ounces oilAmount = (fuel / ratio) * 128; resultUnit = "fl oz (US Fluid Ounces)"; oilResult.innerHTML = oilAmount.toFixed(2) + " " + resultUnit; } summary.innerHTML = "To achieve a " + ratio + ":1 ratio with " + fuel + " " + unit + " of gas."; resultArea.style.display = "block"; }

Understanding Two-Stroke Fuel Ratios

Two-stroke engines, commonly found in chainsaws, weed whackers, outboards, and dirt bikes, do not have a dedicated oil reservoir like a car engine. Instead, they rely on oil mixed directly into the fuel to lubricate the crankshaft, connecting rod, and cylinder walls. Using the correct ratio is critical: too little oil leads to engine seizure, while too much oil causes carbon buildup, "plug fouling," and excessive smoke.

Common Mixing Ratios

• 50:1 Ratio: Standard for most modern high-quality handheld power tools (Stihl, Husqvarna). It uses approximately 20ml of oil per liter of gas.
• 40:1 Ratio: Often used in slightly older equipment or high-performance racing engines that require extra lubrication.
• 32:1 Ratio: Common for vintage engines or during the "break-in" period of a new two-stroke engine.

How to Use This Calculator

1. Select your Fuel Volume: Enter the amount of gasoline you have purchased or plan to mix.
2. Choose Unit: Toggle between Liters (Metric) or US Gallons (Imperial).
3. Enter Ratio: Input the ratio recommended by your engine manufacturer. Only enter the first number (e.g., for 50:1, enter 50).
4. Calculate: The tool will instantly provide the exact amount of oil needed in milliliters or fluid ounces.

Calculation Examples

To help you verify your mix, here are some standard reference points:

Fuel Amount	Ratio	Oil Required
5 Liters	50:1	100 ml
1 US Gallon	40:1	3.2 fl oz
2 Liters	32:1	62.5 ml

Pro Mixing Tips

For the best engine life, always use fresh, stabilized gasoline (ideally ethanol-free) and a high-quality JASO FD-rated two-stroke oil. Always pour the oil into the mixing container first, then add the gasoline; this helps the oil disperse more evenly. Shake the container vigorously before every use, as oil can settle over time.