Quick outboard mix tool: 50:1 is 2.56 oz per gallon (20 ml per liter). Enter gallons or liters to calculate oil in ounces and ml.
Calculate the exact oil quantity for your fuel-to-oil ratio
Always follow your engine manufacturer's recommended ratio. Use TC-W3 marine oil.
Quick reference chart for common outboard ratios. Use the calculator above for any fuel amount.
| Ratio | Oil / 1 gallon | Oil / 1 liter | Oil / 5 gallons |
|---|---|---|---|
| 50:1 | 2.56 oz (76 ml) | 20 ml | 12.8 oz (379 ml) |
| 40:1 | 3.2 oz (95 ml) | 25 ml | 16 oz (473 ml) |
| 32:1 | 4 oz (118 ml) | 31 ml | 20 oz (591 ml) |
| 25:1 | 5.12 oz (151 ml) | 40 ml | 25.6 oz (757 ml) |
| 100:1 | 1.28 oz (38 ml) | 10 ml | 6.4 oz (189 ml) |
Always follow the outboard manufacturer manual or cowling sticker. Break-in and older engines may require richer mixes.
A 2-stroke oil mix ratio tells you how much oil to add to your fuel for proper engine lubrication. Unlike 4-stroke engines that have a separate oil reservoir, 2-stroke outboards burn oil mixed directly with gasoline.
Getting the ratio wrong can cause serious engine damage. Too little oil leads to overheating and seizure. Too much oil causes fouled spark plugs, carbon buildup, and excessive smoke.
The formula is straightforward:
For liters: Oil (ml) = Fuel (liters) × 1000 ÷ Ratio
For example, to mix 5 gallons of fuel at 50:1:
Our calculator handles the math instantly. Enter gallons or liters, select your ratio, and get exact measurements in both fluid ounces and milliliters.
Pro tip: Always mix in a separate container, not directly in your tank. This ensures proper blending before the fuel reaches your engine.
Most modern premix 2-stroke outboards run 50:1 (2.56 oz oil per gallon, or 20 ml per liter). That includes many later Mercury, Yamaha, Suzuki, Tohatsu, and similar marine engines—but the cowling sticker and owner's manual always win over a generic chart.
Do not invent a richer mix “just to be safe” long term, and never run leaner than specified.
Not all 2-stroke oils are created equal. For marine engines, always use TC-W3 certified oil — this certification ensures the oil meets outboard-specific requirements.
For older engines, stick with mineral or semi-synthetic oils at richer ratios (25:1 to 40:1). Modern outboards with oil injection or leaner ratios (50:1 to 100:1) benefit most from synthetic formulas.
Always check your owner's manual for the manufacturer's recommended oil type and ratio.
Oil first, then fuel, then a gentle swirl — the same method works for liters at any ratio.
For a typical 50:1 outboard mix, measure 2.56 oz (76 ml) of TC-W3 oil per gallon of gas — or 20 ml per liter. Use the calculator above for other amounts and ratios.
Add the measured marine oil to a clean fuel can before the gasoline. Oil first ensures the fuel flowing in helps blend the mix.
Pour in the gasoline, then swirl the can gently to combine. Do not shake hard. The mix is ready to use; avoid storing premix longer than about 30 days.
Your 2-stroke outboard engine relies on oil mixed directly into the fuel for lubrication. Unlike 4-stroke engines with a separate oil reservoir, 2-strokes burn oil with every combustion cycle. Too little oil causes overheating, premature wear, and potentially catastrophic engine seizure. Too much oil leads to fouled spark plugs, carbon deposits, and excessive smoke. Getting the ratio right protects your engine and keeps it running at peak performance.
Always use TC-W3 certified marine 2-stroke oil for outboard engines. This certification ensures the oil meets specific standards for water-cooled engines, including proper lubrication at high RPMs, resistance to rust and corrosion, and minimal carbon deposit formation. Never use automotive 2-stroke oil designed for lawn equipment — it lacks the marine-specific additives your outboard needs.
Oil ratios like 50:1 or 25:1 tell you how many parts fuel to one part oil. A 50:1 ratio means 50 parts gasoline to 1 part oil — this is the most common ratio for modern outboards. Older engines and break-in periods often require richer mixes like 25:1 or 32:1 for extra lubrication. Your owner's manual specifies exactly which ratio your engine requires.
You can buy pre-mixed 2-stroke fuel from marine stores, but it's significantly more expensive than mixing your own. A gallon of pre-mixed fuel costs $20-30, while mixing your own costs under $5 per gallon. For regular boaters, self-mixing saves hundreds of dollars per season. Our calculator makes self-mixing foolproof by giving you exact measurements every time.
At 50:1, add 2.56 fluid ounces (about 76 ml) of TC-W3 2-stroke oil per gallon of gasoline. For 5 gallons at 50:1, use 12.8 oz. Use the calculator above for gallons or liters at any ratio.
For a 50:1 ratio, add 20 ml of oil per litre of fuel. For 25:1, add 40 ml per litre. For 40:1, add 25 ml per litre. Switch the calculator unit to liters to get exact ounces and milliliters for any tank size.
If you must err, slightly too much oil is safer than too little. Too little oil causes metal-on-metal contact, overheating, and can seize an outboard permanently. Too much oil fouls plugs and smokes more — annoying but usually fixable. Always aim for the manufacturer ratio with TC-W3 marine oil.
Yes. Use TC-W3 certified marine 2-stroke oil in water-cooled outboards. Automotive or lawn-equipment 2-stroke oil lacks marine corrosion and deposit control additives and is not a substitute.
Neither is universally better — use the ratio on your outboard cowling or in the owner’s manual. 50:1 is standard for most modern premix outboards. 40:1 or richer mixes are common on older engines or during break-in. Using the wrong ratio can void warranty coverage and risk engine damage.
For a 50:1 mix, add 2.56 fluid ounces of 2-stroke oil to 1 gallon of gas. For 5 gallons, add 12.8 ounces.
Yes. Enter fuel in gallons or liters, choose your mix ratio (default 50:1), and get oil in ounces and milliliters for premix 2-stroke outboards. Always use TC-W3 marine oil.
Too lean (not enough oil): Engine runs hot, acceleration feels weak, spark plug electrode looks white/glazed, possible scoring on piston. Too rich (too much oil): Excessive blue/white smoke, fouled spark plugs (black/oily), sluggish acceleration, carbon buildup on exhaust ports. Check your spark plug color regularly — tan/light brown indicates correct mixture.
Use a clean, dedicated fuel container. Add the measured oil first, then pour in gasoline — the fuel flowing in helps mix the oil. Swirl gently to combine. Never mix more than you'll use in 30 days. Always use fresh fuel (less than 30 days old) and TC-W3 certified marine oil.
For 50:1 ratio: 5.12 oz (about 5 oz). For 40:1: 6.4 oz. For 25:1: 10.24 oz (about 10 oz). Our calculator gives you precise measurements and also converts to milliliters for easier measuring with metric containers.
A gentle swirl before fueling is fine, but vigorous shaking is unnecessary and can introduce air bubbles. If properly mixed initially, the oil stays suspended in the gasoline. If fuel has been sitting for more than a few days, a gentle swirl ensures even distribution before pouring into your tank.
For 50:1: approximately 76ml per gallon. For 40:1: approximately 95ml per gallon. For 25:1: approximately 151ml per gallon. Milliliters are more precise for measuring, especially with smaller fuel quantities.
Yes. Pre-mixed 2-stroke fuel should ideally be used within 30 days for best performance. After 60 days, fuel begins to degrade noticeably. Never use fuel older than 90 days — it causes hard starting, poor performance, and can damage engine components. Add fuel stabilizer if storing premix longer than 30 days.
No. Automotive 2-stroke oil (for chainsaws, lawn equipment) is designed for air-cooled engines and lacks the marine-specific additives your water-cooled outboard needs. Always use TC-W3 certified marine 2-stroke oil to prevent corrosion, ensure proper lubrication, and protect against water contamination.
Running straight gasoline (no oil) in a 2-stroke engine causes immediate damage. Without oil, the piston and cylinder walls have no lubrication, leading to extreme friction, overheating, and seizure — often within minutes. This type of damage is not repairable and requires a complete engine rebuild or replacement.
Explore our maintenance guides for more tips on outboard care.
Browse Maintenance GuidesLast Updated:
Reviewed by Premium Boatcare Team