25:1 Gas Oil Mix Calculator

A 25:1 gas-oil mix means 25 parts of gasoline to 1 part of 2-stroke oil. For example, 1 US gallon of gas requires 5.12 fluid ounces of oil, or 1 liter of gas needs 40 milliliters of oil. This is twice as much oil as a 50:1 ratio.

Use 25:1 only for older equipment manufactured in the 1970s-1980s, vintage engines using mineral oil, or when specifically required by your owner's manual. Modern engines designed for synthetic oil typically require 50:1. Using 25:1 on modern engines causes excessive smoke and carbon buildup.

For 5 liters of gasoline at a 25:1 ratio, you need 200 milliliters (mL) of 2-stroke oil.

For 1 US gallon of gasoline at a 25:1 ratio, you need 5.12 fluid ounces (fl oz) of 2-stroke oil.

Older 2-stroke engines from the 1970s-1980s used mineral-based oils that required more oil for adequate lubrication. Engine metallurgy and tolerances were different, and the extra oil helped prevent wear and seizure. Modern synthetic oils provide better lubrication, allowing leaner ratios like 50:1.

No, do not use 25:1 in modern engines designed for 50:1. The excess oil will cause excessive smoke, carbon buildup on pistons and spark plugs, reduced performance, and potential engine damage. Always follow your manufacturer's recommended ratio.

For vintage engines originally designed for 25:1, use high-quality 2-stroke oil. While these engines were designed for mineral oil, modern synthetic or semi-synthetic 2-stroke oils provide better protection. Always check your owner's manual for oil type recommendations.

Yes, 25:1 produces significantly more smoke because it contains twice as much oil as 50:1. This is normal for the ratio but can be excessive and unpleasant. The extra oil also creates more carbon deposits in the exhaust system and on spark plugs.

Do NOT convert ratios without consulting a mechanic. Older engines designed for 25:1 may not receive adequate lubrication at 50:1, leading to engine seizure. If you want to use modern synthetic oil at a leaner ratio, consult with a small engine specialist first.

Like any premixed 2-stroke fuel, 25:1 mix should be used within 30 days for best results. Use fresh gasoline and consider adding a fuel stabilizer if you need to store it longer. Always shake the container before use to ensure the oil and gas remain mixed.