Short answer: 25 to 1 means 5.12 fl oz of two stroke oil per gallon of regular unleaded. Pour the oil into the can first, then the gas, then shake it. Never run straight gas in a two stroke.
The mixing chart
| Gas | Two stroke oil at 25 to 1 |
|---|---|
| 1 quart (32 oz) | 1.3 oz |
| Half gallon | 2.6 oz |
| 1 gallon | 5.12 oz |
| 2 gallons | 10.2 oz |
| 2.5 gallons | 12.8 oz |
| 5 gallons | 25.6 oz |
The maths is simple if you ever need a size that is not on the chart. A gallon is 128 oz, and 128 divided by 25 is 5.12.
What to actually buy
- Gas: regular unleaded, 87 octane. You do not need premium and it will not make the bike faster. Get it fresh, do not use the can that has been in the shed since last summer.
- Oil: any two stroke engine oil from an auto parts store, a hardware store or a gas station. Look for the words TWO STROKE or 2 CYCLE on the bottle. A single bottle mixes a lot of tanks and lasts most families a whole season.
Do not use: motor oil, car oil, 10W30, chainsaw bar oil, or anything that does not say two stroke on it. Those do not burn the way two stroke oil does and they will gum up the engine.
How to mix it, step by step
- Get a clean gas can. Label it, because mixed fuel should never end up in a lawnmower or a car.
- Oil goes in first. Measure 5.12 oz for a gallon and pour it into the empty can. Oil first matters, it mixes far better than pouring oil on top of gas.
- Add one gallon of fresh unleaded on top.
- Cap it and shake it properly, twenty or thirty seconds. Gently rocking it does not cut it, the oil is heavier and sits at the bottom.
- Give it a shake again every time before you fill the bike.
There is a small bottle in the box
Every bike we ship comes with a small premix bottle so you are not stuck the day it arrives. Use that to get the first tank going, then pick up a full bottle of two stroke oil at any auto parts store for the rest of the season. It is a few dollars.
What happens if you get it wrong
Too much oil (say 16 to 1). The bike smokes heavily, bogs down, will not rev out cleanly, and it fouls the spark plug. Annoying, and it usually means cleaning or replacing the plug, but it will not destroy the engine. If yours is smoking and you want to work out whether it is the mix or something else, read why a two stroke smokes and how to read the colour.
Too little oil (say 50 to 1). This is the dangerous one. The engine runs hotter than it should and the moving parts lose their lubrication. It might seem fine for a while and then seize.
Straight gas, no oil at all. The engine seizes, and usually fast. A two stroke has no oil sump, every drop of lubrication it gets comes from the oil mixed into the fuel. This is the single most expensive mistake anyone makes with one of these bikes, and it is not a warranty repair, because it is not a defect.
Fuel is behind most running problems
If the bike is misbehaving, start here before you touch anything mechanical. Bad or old fuel causes most of it.
- Will not start at all: work through the will not start checklist in order.
- Fires and then dies after a few seconds: that is a carburetor problem, usually a blocked pilot jet, and stale fuel is what blocks it.
- Running rich, fouling plugs or bogging at part throttle: check the air filter next, because a clogged one behaves a lot like a bad mix.
Common questions
How do I measure 5.12 oz?
Most two stroke oil bottles have measuring marks right on the side. If yours does not, a cheap measuring cup from the dollar store works. Slightly over is safer than under.
Can I just eyeball it?
No. Eyeballing is how engines seize. It takes ten seconds to measure.
How long does mixed fuel last?
About 30 days. After that it starts to break down and you get hard starting and poor running. Mix what you will actually use. For most families that is a gallon at a time. If the bike is going away for the season, drain it properly first: how to store a dirt bike for winter.
Is 25 to 1 the same as 40 to 1 or 50 to 1?
No, and this matters. Other bikes run other ratios. Ours is 25 to 1. Do not use a ratio you read about for a different bike.
What if I already ran straight gas?
Stop riding it immediately. Drain the tank, mix proper fuel, and send us a video of it running at pluggedbycc@gmail.com so we can hear what it sounds like before you put more hours on it.
Do the electric bikes need this?
No. The electric bikes have no gas and no oil to mix at all. You plug them in. That is one of the main reasons people step up to them, the Sykeruns X5 for teens and the Sykeruns X7 for adults. The equivalent job on an electric is looking after the pack, which we cover in how to charge an electric dirt bike battery and make it last.
Next steps
Got your fuel mixed and ready to fire it up? Read how to start a 50cc dirt bike next, because the cold start order trips up more people than the fuel does.
The full fuel guide, the assembly video and the maintenance checklist are all free at manual.pluggedby50cc.com.
Off road use only. Helmet and gear every ride, and an adult supervising.
Plugged by 50CC is an independent retailer. We do not manufacture, assemble, modify or service the bikes we sell. Every bike ships sealed in its factory crate exactly as it reaches us, about 90% assembled from the factory, and final assembly and setup are completed by the buyer. Off-road use only. Riders under 18 should always be supervised by an adult.