2-Stroke Dirt Bike Oil Mix: Premix Ratio Chart by Bike

The 2-stroke dirt bike oil mix is not one number. The Japanese manufacturers have printed figures around 32:1 for decades, which is 4 oz of 2-stroke oil per US gallon. KTM’s two-stroke manuals give a range of 40:1 to 60:1 with a high-grade oil, and say to use 40:1 when in doubt. Most riders end up between 32:1 and 40:1, and the right answer for your bike is the figure in its manual with the oil it names, kept consistent so the jetting stays right.

That is the honest answer to a question that forums turn into arguments. The rest of this guide is the detail behind it: what each brand prints, how much oil each ratio is in a real fuel jug, what “2%” means, and when a bike needs no premix at all.

Dirt bike premix ratio by brand

Bike	What the manual says	In oz per gallon
Yamaha YZ65, YZ85, YZ125, YZ250	About 30:1 to 32:1 with Yamalube 2-R	4.27 to 4 oz
Honda CR80 to CR500 (discontinued)	32:1 with Pro Honda HP-2	4 oz
Kawasaki KX and Suzuki RM two-strokes	Around 32:1 in most model years	4 oz
KTM SX, XC and carbureted EXC	40:1 to 60:1 with a high-grade oil, 40:1 if unsure	2.13 to 3.2 oz
Husqvarna TC/TE and GasGas MC/EC (KTM platform)	Same as the KTM they share an engine with	2.13 to 3.2 oz
KTM/Husqvarna/GasGas TPI and TBI, oil-injected Beta	No premix in the fuel tank (oil injection)	none
Yamaha PW50, PW80	No premix: Autolube oil injection	none

Two cautions on the table. First, these are the figures as they have appeared in owner’s manuals across model years, and a manual for a specific year can differ, so read yours: the ratio is usually in the fuel section and on a sticker near the tank. Second, the ratio in a manual is paired with a named oil. A KTM manual’s 60:1 assumes a fully synthetic premix oil of the grade it names. With a cheaper oil the same manual moves you richer.

Older and vintage bikes are their own category. Bikes from the 1970s and early 1980s often called for 20:1 on the mineral oils of the day, and builders of rebuilt or ported engines frequently specify their own ratio. When an engine builder gives you a number, that number beats the original manual.

Premix chart: 32:1 to 60:1

Every figure here is oil = gas ÷ ratio, the same arithmetic the calculator uses.

Gas	32:1	40:1	50:1	60:1
1 US gallon	4 oz	3.2 oz	2.56 oz	2.13 oz
2 US gallons	8 oz	6.4 oz	5.12 oz	4.27 oz
5 US gallons	20 oz	16 oz	12.8 oz	10.67 oz
1 litre	31.25 ml	25 ml	20 ml	16.67 ml
5 litres	156.25 ml	125 ml	100 ml	83.33 ml
10 litres	312.5 ml	250 ml	200 ml	166.67 ml

The 5-gallon row explains a lot of pit-area habits. A 16 oz bottle of premix oil into 5 gallons of race or pump gas is 40:1 almost exactly (16 oz), which is why “one bottle per jug” is such a common routine. A 32:1 rider pouring the same bottle into 5 gallons is actually running 40:1 and may not know it.

For odd amounts, such as the last 0.7 gallons in the jug, use the calculator:

Fuel → oil / Oil → fuel

Fuel → oil Oil → fuel

Amount of fuel

Gallons (US) Litres

Equipment (optional) Choose equipment… Chainsaw (50:1) String trimmer / weed eater (50:1) Leaf blower (50:1) 2-stroke lawn mower (50:1) Dirt bike / motorcycle (40:1) Outboard motor (50:1)

Mix ratio

100:1 50:1 40:1 32:1 25:1 20:1

Custom ratio (X : 1)

Calculate Reset Copy link to this mix

Add this much oil

16 oz

≈ 473.18 ml

Add 16 oz of 2-stroke oil to 5 gal of gas at a 40:1 ratio.

What “2%” and the other percentages mean

European manuals and a lot of riders talk in percentages. The percentage is the oil as a share of the gas, so it converts straight to a ratio:

• 1.7% is 60:1 (16.67 ml per litre)
• 2% is 50:1 (20 ml per litre)
• 2.5% is 40:1 (25 ml per litre)
• about 3.1% is 32:1 (31.25 ml per litre)
• 4% is 25:1 (40 ml per litre)

A rider who says “I run 2%” is running 50:1, which is leaner than every Japanese manual and at the lean end of KTM’s range. On a modern synthetic in a trail bike that can be fine. On a 125 that lives at the rev limiter, most tuners would move it richer.

Why bikes run richer than trimmers

Trimmers, saws and blowers almost all run 50:1 on the same oil. A dirt bike engine sees a much wider and harsher load: full throttle in third gear up a hill, then closed throttle down the other side with the engine braking and almost no fuel, and therefore almost no oil, going through it. The bottom end, the big-end bearing and the piston skirt get their oil only from the fuel passing through, so a richer premix gives more margin through those closed-throttle stretches and at sustained high rpm.

The other difference is that a bike is jetted, and the ratio is part of the jetting. Oil takes up space in the fuel, so more oil means slightly less gasoline per unit of volume through the same jet. Going from 40:1 to 32:1 leans the air-fuel mixture a little; going from 32:1 to 50:1 richens it. Neither is dramatic in one step, but a rider who changes ratio and then fights a bog or a pinging top end is often chasing the change they just made. The dirt bike page covers reading the plug and the power valve to check where you are.

Mixing at the truck

Most dirt bike fuel is mixed in a hurry, on a tailgate, with dirty gloves. The routine that keeps the ratio honest:

1. Use one jug per ratio and label it. If you also run a 50:1 trimmer at home, keep that can separate. A trimmer on 32:1 is merely smoky; a 125 on 50:1 meant for the trimmer is the expensive mistake.
2. Measure in a ratio bottle or cup. A ratio-rite style cup has scales for each ratio and amount of gas, so you read the line instead of doing arithmetic. The measuring tools guide compares the options.
3. Oil first, then gas. Pour the oil into the empty jug and fill it at the pump; the stream mixes it.
4. Shake before every fill-up. Oil settles in a jug that has ridden in the truck all week.
5. Mix what you will ride. Pump premix with ethanol is at its best for about a month. Race fuel keeps longer sealed, but once mixed and opened treat it the same way.

Oil choice matters more than the last few points of ratio

A good full-synthetic premix oil at 40:1 protects better than a cheap mineral oil at 32:1. For an air-cooled or liquid-cooled MX engine, look for an oil rated JASO FD or a racing premix oil made for high-rpm two-strokes. Castor-blend oils such as Maxima Castor 927 and Klotz Super Techniplate are a racing tradition: excellent film strength at heat, at the cost of more residue in the power valve and pipe, which is a fair trade on a race bike that gets rebuilt often and a poor one on a trail bike.

Two oils to keep out of the jug: marine TC-W3 oil, which is made for water-cooled outboards running much cooler, and four-stroke motor oil, which is not designed to burn and will carbon up the exhaust port and power valve. The TC-W3 vs JASO FD guide explains the difference, and synthetic vs conventional covers whether you can switch oils between tanks.

Bikes that need no premix

Oil-injected two-strokes take straight gas in the fuel tank and 2-stroke oil in a separate reservoir. That covers the Yamaha PW50 and PW80 kids’ bikes (Autolube), KTM, Husqvarna and GasGas TPI and TBI fuel-injected enduro models, and Beta’s oil-injected enduro bikes. Premixing on top of the injection does not add protection; it doubles the oil, fouls plugs and smokes. Read the manual for break-in, since some injected models ask for a premixed first tank, and above all keep the oil reservoir full. An injected bike with an empty oil tank seizes like a premix bike run on straight gas.

Lean, rich, or right

• Right: a tan to light brown plug insulator, a light haze from the pipe when cold, and a clean throttle response through the range.
• Too rich (too much oil or too rich a jet): black, wet plugs, spooge dripping from the silencer joint, a bike that loads up on slow trail sections.
• Too lean (too little oil, or jetting gone lean): a white or glazed plug, pinging under load, a top end that suddenly feels tight. Stop before it becomes a seized or holed piston.

If you are unsure of your ratio, use the richer of the two numbers you are deciding between and jet for it. The cost of too much oil is a plug and some cleaning. The cost of too little is a top end.

For the general mixing rules that apply to everything with a two-stroke engine, see how to mix 2-stroke fuel, and the reference pages for 32:1, 40:1 and 50:1 have the full charts. When the bike goes away for the winter, the winterizing guide covers draining the float bowl and what to do with the leftover jug.