Fuel Premix Calculator

Calculate the exact oil-to-gas ratio for your 2-stroke engine

US Gallons Liters

: 1

Example: Enter "50" for a 50:1 ratio.

Mixing Results:

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How to Use the Fuel Premix Calculator

This calculator is designed for owners of 2-stroke engines found in dirt bikes, chainsaws, leaf blowers, and outboard boat motors. Unlike 4-stroke engines, these machines require oil to be pre-mixed directly into the gasoline to ensure the internal components are properly lubricated during operation.

Understanding the Ratio

A mixing ratio like 50:1 means you use 50 parts of gasoline for every 1 part of 2-stroke oil. Common industry ratios include:

• 32:1 – Common for high-performance motocross bikes or older machinery.
• 40:1 – Standard for many modern chainsaws and string trimmers.
• 50:1 – Typical for most modern handheld power equipment and outboards.
• 100:1 – Specifically for high-efficiency engines designed for lean oil mixtures.

Realistic Example

If you have a 5-gallon gas can and your equipment requires a 40:1 ratio:

1. Input "5" in the Fuel Amount field.
2. Select "US Gallons" as the unit.
3. Input "40" in the Mixing Ratio field.
4. The calculator will determine you need exactly 16 fluid ounces of oil to achieve the perfect mix.

Why Accuracy Matters

Mixing fuel is a science that affects your engine's longevity:

• Too Little Oil (Lean Mix): This causes excessive heat and friction, which can lead to "seizing" the engine and permanent damage.
• Too Much Oil (Rich Mix): This leads to carbon buildup on the piston, "fouled" spark plugs that won't fire, and excessive blue smoke from the exhaust.

function calculatePremix() { var fuelAmount = parseFloat(document.getElementById("fuelAmount").value); var fuelUnit = document.getElementById("fuelUnit").value; var mixRatio = parseFloat(document.getElementById("mixRatio").value); var resultDiv = document.getElementById("premixResult"); var oilDisplay = document.getElementById("oilDisplay"); var summaryText = document.getElementById("summaryText"); if (isNaN(fuelAmount) || fuelAmount <= 0) { alert("Please enter a valid fuel amount."); return; } if (isNaN(mixRatio) || mixRatio <= 0) { alert("Please enter a valid mixing ratio."); return; } var oilAmount; var resultUnit; if (fuelUnit === "gallons") { // 1 US Gallon = 128 Fluid Ounces var totalOunces = fuelAmount * 128; oilAmount = totalOunces / mixRatio; resultUnit = "fl oz"; oilDisplay.innerText = oilAmount.toFixed(2) + " Fluid Ounces of Oil"; summaryText.innerText = "To mix " + fuelAmount + " gallons of gasoline at a " + mixRatio + ":1 ratio, add " + oilAmount.toFixed(2) + " oz of 2-stroke oil."; } else { // 1 Liter = 1000 Milliliters var totalMilliliters = fuelAmount * 1000; oilAmount = totalMilliliters / mixRatio; resultUnit = "ml"; oilDisplay.innerText = oilAmount.toFixed(0) + " ml of Oil"; summaryText.innerText = "To mix " + fuelAmount + " liters of gasoline at a " + mixRatio + ":1 ratio, add " + oilAmount.toFixed(0) + " ml of 2-stroke oil."; } resultDiv.style.display = "block"; resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }