2 Stroke Premix Ratio Guide: OEM Ratios, Mixing Chart And 32:1 vs 40:1

The Short Answer

The right 2 stroke premix ratio is the one printed in your owner's manual, and on modern bikes it varies more than most riders expect. Current KTM, Husqvarna and GASGAS 125s call for 1:40. Their 250 and 300 premix bikes call for 1:60. Yamaha's 2026 YZ125 and YZ250 manuals list a premix ratio of 30:1 with Yamalube 2R. Several enduro 300s (KTM 300 XC-W, Husqvarna TE 300, Beta 300 RR) do not use premix at all because they have oil injection.

If you only need the numbers, jump to the mixing chart below or use our premix ratio calculator, which works in gallons, liters, ounces and milliliters. The rest of this guide explains where those numbers come from, how to mix accurately, and what the 32:1 vs 40:1 debate actually changes.

Ratios in this guide are written the way each manufacturer prints them. KTM group manuals write 1:40 (one part oil to 40 parts fuel). Yamaha writes 30 under "Premix ratio," meaning 30 parts fuel to one part oil. Same idea, different order.

OEM Premix Ratios By Model

We pulled these straight from the current owner's manuals. Click a model to open the manufacturer's PDF. Octane figures are the Research Octane Number (RON) used in KTM group and Beta manuals. US pumps show the lower (R+M)/2 number, so a RON 95 spec is roughly a 91 at a US pump and RON 98 sits a few points higher. Husqvarna's TE 300 manual prints that conversion itself: "ROZ 95/RON 95/PON 91."

Two things stand out. First, the same family of bikes can use different ratios: a 2026 KTM 125 SX is 1:40 on 98 octane, while the 250 SX and 300 SX are 1:60 on 95 octane. Second, "300" no longer tells you whether a bike is premix. The 2026 GASGAS EX 300 manual lists 1:60 premix, while the Husqvarna TE 300 and KTM 300 XC-W run oil injection and their manuals say plainly: "Do not refuel using pre-mixed fuel."

For model-specific service intervals, see our KTM 125 SX, KTM 250 SX, KTM 85 SX, KTM 300 XC-W, Husqvarna TC 125, TC 250, TE 300, GASGAS MC 125, EX 300, Yamaha YZ125, YZ250 and Beta 300 RR schedule pages.

Premix Mixing Chart: Ounces And Milliliters

The math is simple: divide the fuel volume by the ratio number. One US gallon is 128 US fluid ounces or 3,785.41 ml, so at 40:1 you add 128 / 40 = 3.2 oz (about 94.6 ml) of oil per gallon. In metric, 1 liter at 40:1 takes 1,000 / 40 = 25 ml.

You can sanity check the chart against KTM's own numbers. The 2026 KTM 125 SX manual lists 10 liters of fuel with 250 ml of 2-stroke oil for 1:40, and the Husqvarna TC 250 manual lists 10 liters with 167 ml for 1:60. Both match the 10 liter column above.

Need an odd amount, like 1.6 gallons to top off a 7.2 liter tank? The MotoMind premix ratio calculator does any volume and ratio in either unit system.

32:1 vs 40:1 (And 50:1 vs 60:1): What Actually Changes

The 32:1 vs 40:1 argument has been going on at every track for decades. Here is what the numbers mean in practice. At 32:1 you add 4.0 oz per gallon. At 40:1 you add 3.2 oz. That is 25 percent more oil at 32:1. Going from 50:1 to 60:1, the oil drops from about 2.56 oz to 2.13 oz per gallon.

• More oil (richer ratio, smaller number) means more oil film on the crank bearings, rod and piston skirt. It also displaces a little fuel, so the effective fuel mixture leans slightly, and it tends to leave more residue on the plug, power valve and exhaust.
• Less oil (leaner ratio, bigger number) burns cleaner and leaves fewer deposits, but the margin for a mixing mistake or a low-quality oil shrinks.

Manufacturers set the ratio together with a specific oil and a specific jetting or fuel map. KTM's 1:60 spec for the 250 and 300 SX assumes a fully synthetic JASO FD oil. Yamaha's 30:1 spec assumes Yamalube 2R. If you change the ratio by a large amount on a carbureted bike, the jetting may need to change too, because oil volume affects how much fuel actually reaches the engine. On fuel-injected 2-strokes, the ECU is calibrated for the specified mix.

Our advice: start with the manual ratio and the oil grade it calls for. If you switch to an oil brand that prints its own recommended ratio for racing, that can be fine, but change one thing at a time and read your spark plug and power valve afterwards. Never go leaner than the manual just to reduce smoke.

Break-In Premix

Several manuals ask for extra oil while a new or rebuilt engine beds in:

• KTM 85 SX: "During the first ten operating hours, refuel with a mixing ratio of 1:30," then return to 1:40.
• Yamaha YZ125 and YZ250: fill the tank with a break-in mixture at a premix ratio of 15 before the first ride, then follow the staged break-in (about 20 minutes at half throttle or less, then about 40 minutes at three-quarters or less, with checks in between).
• Beta 300 RR: even with oil injection, the first refuel is a 1% premix for the 200, 250 and 300 (3% for the RR 125), and Beta says to repeat the break-in whenever the piston, rings, cylinder or crank parts are replaced.

After a top end rebuild, follow the same break-in your manual gives for a new engine.

Which 2-Stroke Oil: JASO FD And Fully Synthetic

KTM, Husqvarna and GASGAS manuals specify 2-stroke engine oil meeting JASO FD, and the refueling instructions in the 125, 250/300 SX and 300 XC-W manuals add "fully synthetic." JASO M345 grades 2-stroke oils on lubricity, detergency, exhaust smoke and exhaust system blocking. FD carries the same requirements as FC but with considerably stricter detergency, which makes it the top grade in that standard. In plain terms, it is the grade designed to keep rings, power valves and exhaust ports cleaner.

Yamaha names Yamalube 2R for the YZ125 and YZ250, and Beta names Liqui Moly Motorbike 2T Synth Offroad Race. If you use another brand, look for the JASO FD rating on the bottle.

Oil injected bikes need oil labeled for separate (injection) lubrication. The KTM 300 XC-W manual says: "Only use 2-stroke oil which is appropriate for separate lubrication," and adds that the oil tank must be filled to at least the upper edge for a full tank of fuel. If the oil warning light comes on, there is enough oil for the remaining fuel in the tank, and you should add oil before the next refuel.

Yamaha's manuals also carry a warning worth repeating: never mix two types of oil in the same batch, because clotting can result. If you change oil brands, drain the fuel tank and the carburetor float bowl first.

How To Mix Premix Accurately

1. Start with fresh fuel of the octane your manual lists. Yamaha's manuals say to use fresh, name-brand gasoline and to mix "the day of the race."
2. Use a ratio-marked mixing bottle or a graduated measuring cup. Guessing "a glug" is how pistons get seized. Do not use the fuel can's gallon marks if they are molded loosely; measure the fuel too.
3. Pour the oil into the can first or with the first part of the fuel, then add the rest of the fuel. This helps the two blend.
4. Close the can and shake it thoroughly before you fill the bike, and give it another shake if it has been sitting.
5. Label the can with the ratio and the date you mixed it, especially if your garage has both 40:1 and 60:1 bikes or a 4-stroke that must never get premix.
6. Do not top off an oil-injected bike with premix unless your manual says to (as Beta does for the break-in tank).

If you run two bikes with different ratios, keep two cans in two colors. It is the cheapest insurance in the sport.

How Long Does Premix Last?

Shorter than most people think, at least by the manufacturers' standards. Yamaha's YZ125 and YZ250 manuals say: "Always use fresh, name-brand gasoline, and mix the oil and gas the day of the race. Do not use premix that is more than a few hours old." That is a racing standard, but it tells you the factory does not want old mix in the engine.

KTM group manuals list a recommended fuel additive (Motorex Fuel Stabilizer) and, in their storage chapters, tell you to add fuel additive on the last refuel before parking the bike and to fill the tank with fuel that has the lowest possible ethanol content. Carbureted models such as the 85 SX also say to empty the float chamber before storage.

Practical rules that follow from the manuals:

• Mix only what you will use in a weekend or so, and use it promptly.
• Store premix in a sealed, approved container out of sunlight.
• Before a long layup, stabilize the fuel or drain it, following our dirt bike winterizing guide.
• When in doubt, dump old mix into a lawn tool or a proper disposal site and mix fresh.

Signs Your Premix Ratio Is Off

Wrong mix rarely announces itself clearly, but these are the common clues:

• Too much oil: a wet or fouled plug, excess smoke, spooge dripping from the silencer, sluggish response and a power valve that gums up quickly.
• Too little oil (or none): the engine may run crisp at first, then you may hear a metallic rattle or feel it tighten or seize. A scuffed piston skirt at the next teardown is the evidence.
• Wrong oil in an injected bike: warning lights or a pump issue rather than a mixture issue. Check the oil tank first.

If the bike suddenly runs differently after a fresh can, suspect the mix before you touch the jetting. Our won't start troubleshooting guide and common troubleshooting guide cover the rest.

Track Fuel, Oil And Top End Hours

Premix is only one part of keeping a 2-stroke healthy. The other part is knowing when the top end, gear oil and air filter are due. MotoMind: Dirt Bike Service is a free iPhone app that logs fuel fill-ups and engine hours, and its GPS ride tracker adds ride time to your bike's hours when you save a ride. With MotoMind Pro you can set your manual's intervals for gear oil and top end service, and the app shows each task as upcoming, due now or overdue.

See our 2-stroke maintenance guide for the full service picture.