32:1 Fuel Mix — Gas to Oil Ratio Calculator & Chart
A 32:1 two-stroke fuel mix means 4 oz of 2-stroke oil for every US gallon of gas, or 31.25 ml of oil per litre. Use the calculator to get the exact amount for any quantity of fuel, then check the full 32:1 mix chart in gallons and litres below. It works the same for "2-cycle", "2-stroke" and "two-stroke" engines — it's all the same premix.
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At 32:1 you add 4 oz of oil per gallon (31.25 ml per litre). For a 5-gallon can of gas that's 20 oz of 2-stroke oil.
Full mix chart
32:1 ratio
| Gallons of gas | oz of oil |
|---|---|
| 0.5 | 2 |
| 1 | 4 |
| 1.5 | 6 |
| 2 | 8 |
| 2.5 | 10 |
| 3 | 12 |
| 4 | 16 |
| 5 | 20 |
| 6 | 24 |
| Litres of gas | ml of oil |
|---|---|
| 1 | 31.25 |
| 2 | 62.5 |
| 3 | 93.75 |
| 4 | 125 |
| 5 | 156.25 |
| 10 | 312.5 |
| 15 | 468.75 |
| 20 | 625 |
| 25 | 781.25 |
Where 32:1 comes from
Thirty-two to one is a vintage-equipment ratio. It shows up on chainsaws from the 1960s through the 1980s (McCulloch, Homelite, Poulan and their contemporaries), on old two-stroke Lawn-Boy mowers, on period motocross and kart engines, on some industrial and rental equipment, and as a common break-in ratio after a cylinder has been rebuilt or replaced.
The reason is historical. Those engines were designed around mineral oils, with looser tolerances and no emissions pressure. Those oils needed more volume to produce the film a modern synthetic produces with less.
The easiest ratio to measure
In US units 32:1 lands on round numbers: 4 oz of oil per gallon, 20 oz for a 5-gallon can, and a 16 oz pint that treats exactly 4 gallons. That is why old shop measuring cups usually carry a 32:1 mark.
In metric it is 31.25 ml per litre, so a 5-litre can takes 156.25 ml of oil.
Running 32:1 in a modern machine
Putting 32:1 through a current 50:1 chainsaw or trimmer rarely breaks anything, but it does make a mess. Expect blue smoke, a spark-arrestor screen that clogs within a few working hours, a plug that fouls sooner, and carbon building on the exhaust port and in the muffler.
If what you actually want is more lubrication margin in a hard-worked machine, the modern answer is not a richer ratio but a better oil at the decal ratio. A quality JASO FD oil at 50:1 protects more than a mediocre oil at 32:1, and it does not plug the exhaust.
Common questions
[01] What is 32:1 in ounces per gallon?
32:1 is 4 fluid ounces of oil per US gallon of gas (128 ÷ 32 = 4).
[02] What is 32:1 in ml per litre?
32:1 is 31.25 ml of oil per litre of gas (1000 ÷ 32 = 31.25).
[03] What happens if I add too much oil at 32:1?
Too much oil makes the engine run rich — it can smoke, foul the spark plug and lose power. A little extra is safer than too little, but stay close to 32:1 and follow your owner's manual.
[04] Why does older equipment use 32:1?
Because it was designed around mineral oils, with looser tolerances and no emissions requirements. Those oils needed more volume to produce the lubricating film a modern synthetic produces with less.
[05] Can I run 32:1 in a modern 50:1 chainsaw?
It rarely damages the engine, but it makes a mess: blue smoke, a clogged spark-arrestor screen, a fouled plug and carbon in the exhaust. A quality JASO FD oil at the decal ratio is the better answer.