Stihl Alkylate Fuel (Mix & Engine Fit Guide)
STIHL MotoMix is a ready-to-use 50:1 alkylate premix for compatible STIHL two-stroke and 4-MIX engines. It already contains two-stroke oil, so do not add more. Check your exact model’s manual before filling: MotoMix is not for battery tools, gasoline-only four-stroke engines, or engines that call for another fuel type or mix ratio.
For years, many owners have mixed fuel at the bench: measure gasoline, add oil, shake, then label the can. That routine still works when the engine manual allows it and the ratio is right. But a ready-mixed alkylate fuel can simplify the job, especially when you are heading out and want to avoid a measuring mistake.
The key is fit, not guesswork. Read the fuel label and the saw’s manual before pouring. A correct fuel choice helps protect the engine, but it will not sharpen a dull chain or fix a lubrication fault. Here is how I check the fuel, fill safely, and sort out common problems.
What STIHL MotoMix is, and which engines it fits
Alkylate fuel is a specially refined gasoline used in some ready-mixed small-engine fuels. STIHL MotoMix is a 50:1 premix: it contains gasoline and the required two-stroke oil in the specified proportion. Confirm that the fuel and ratio match your machine’s manual before use.
MotoMix is intended for compatible STIHL two-stroke and 4-MIX engines. The word “compatible” matters: do not assume every STIHL engine takes the same fuel. Check the operator’s manual for your exact model, especially if the tool is older or has been modified.
It is not the right fuel for a gasoline-only four-stroke engine, a battery tool, or an engine whose manual specifies a different fuel or oil ratio. If you cannot confirm the requirement, pause and look up the model number rather than testing a guess in the tank.
| Engine requirement in the manual | What to use |
|---|---|
| STIHL two-stroke, 50:1 premix | MotoMix, if the manual permits it |
| STIHL 4-MIX, 50:1 premix | MotoMix, if the manual permits it |
| Gasoline-only four-stroke | Fuel specified by that engine’s manual, not MotoMix |
| Battery-powered equipment | No fuel |
| Different mix ratio or fuel specification | Follow the manual; do not assume MotoMix fits |
Next step: Find the model number and fuel specification in the manual or on the manufacturer’s official product information. Fuel choice does not set bar length, chain pitch, chain gauge, drive links, chain speed, or engine speed; those remain model-specific.
50:1 mix ratio: what it means for MotoMix and regular fuel
A 50:1 ratio means 50 parts gasoline to one part two-stroke oil by volume. MotoMix already has oil blended at this ratio, so it is ready to pour into a compatible engine’s fuel tank. Adding more oil changes the specified mixture.
This is one place where a careful habit prevents a costly error. I check the label before filling, even when I have used the same can before. A shop container can hold a different fuel, and a premix can looks much like a gasoline can once it is off the shelf.
If you are making fresh 50:1 fuel yourself, the oil quantities below show the equivalent ratio. They are not instructions to add oil to MotoMix.
| Gasoline amount | Two-stroke oil for 50:1 |
|---|---|
| 1 L | 20 mL |
| 5 L | 100 mL |
| 10 L | 200 mL |
| 1 US gallon | About 2.6 US fluid ounces |
Do not pour extra oil into MotoMix. Also, never run straight gasoline in an engine designed for a gasoline-and-oil mix. The oil supplies engine lubrication; the wrong mixture can lead to rapid wear and engine damage.
How to check fit and refuel safely
A fuel check confirms the engine’s required fuel type and ratio, while a refueling check helps keep dirt, spills, and ignition sources away. I use the same sequence each time: verify the label, inspect the saw, then refuel with the engine stopped and cool.
- Check the manual and fuel can. Confirm the model accepts the fuel and that the premix ratio matches. Check that the can is clean, clearly labeled, and within the fuel maker’s stated storage guidance.
- Inspect the saw. Look for fuel or oil leaks, damage around the cap, and debris that could fall into the tank. Do not use a saw with a suspected leak until it has been checked.
- Refuel safely. Stop the engine and allow it to cool. Keep fuel away from flames, sparks, and hot surfaces. Use an approved, labeled container and avoid spilling fuel on the saw or ground.
- Close the cap and move away. Before restarting, move away from the fueling point. Follow your model’s cold- or warm-start procedure, with the chain brake engaged and the bar and chain clear.
Use the correct bar-and-chain oil in its own tank. Premix is engine fuel, not chain lubricant. After starting, verify that the chain receives bar oil as the manual directs. A lack of oil delivery needs attention before cutting.
For cutting, check the chain brake, throttle lockout, chain catcher, throttle trigger, bar, and chain tension. Wear suitable head, eye or face, hearing, leg, hand, and foot protection. Keep others clear, plan escape routes, and assess the work before cutting. Tree felling and other high-risk work call for trained, qualified people. Follow applicable safety rules, including OSHA requirements where they apply, and ANSI Z133 guidance for arboricultural work.
Practical fuel-fit scenarios and troubleshooting
These examples are common decision points, not claims about a particular customer or machine. They show how I would work through a fuel question without using the tank as a test bench. The model’s manual and the fuel label remain the authority.
Scenario: A saw owner has a can of MotoMix and a 50:1 STIHL two-stroke saw. The owner checks the manual, confirms the fuel type and ratio, checks the can label, then fills without adding oil. If the saw runs poorly afterward, the first step is not to change the carburetor setting.
Scenario: A tool is marked 4-MIX. The owner checks the exact manual rather than assuming that “four-stroke” means gasoline only. Some 4-MIX engines use a fuel-and-oil mix; use MotoMix only if that model’s instructions specify a compatible premix and ratio.
Scenario: The machine manual calls for a different ratio or straight gasoline. Do not use MotoMix by assumption. Choose the fuel specified for that engine. If the manual is missing or the model is unclear, identify the model before filling.
If the saw starts but runs poorly, check that the fuel is correct and fresh, that the tank and cap area are clean, and that there are no leaks. Do not alter carburetor settings solely because you switched to alkylate fuel. If operation remains abnormal, use the model’s service procedure or have a qualified technician inspect it.
If a chain cuts slowly, fuel is only one possible issue. A dull chain can burn wood and place extra load on the saw. Stop and inspect the chain, tension, and bar-oil delivery; sharpen with the file size and angles specified for that chain. Do not force a dull chain through the cut.
Storage and seasonal fuel care
Storage guidance depends on the fuel product and the engine. Follow the instructions on the MotoMix container and in the operator’s manual; do not rely on a general shelf-life claim in place of the label. Keep fuel in its approved container, away from heat and ignition sources.
For extended storage, use the engine manual’s fuel-system procedure. Clean the saw, protect the bar and chain, and store the machine securely. Do not assume that fuel described as long-lasting removes the need to prepare the tool for storage.
Keep fuel containers closed and labeled so premix cannot be mistaken for straight gasoline. If you are unsure what is in a container, do not put it in the saw. Dispose of old or unwanted fuel according to local requirements rather than pouring it onto the ground or into a drain.
Quick answers about STIHL alkylate premix
These short answers cover the checks owners most often need before filling. The manual for your exact machine and the fuel container’s directions take priority if they differ from general guidance.
Can I use STIHL MotoMix in any STIHL chainsaw?
No. Check that the exact model’s manual allows the fuel and its 50:1 ratio.
Do I add two-stroke oil to MotoMix?
No. It is already blended with oil. Adding more changes the specified ratio.
Is MotoMix 50:1?
Yes. STIHL identifies MotoMix as a 50:1 premix for compatible engines.
Can I use it in a STIHL 4-MIX engine?
Use it only if that model’s manual specifies a compatible 50:1 premix.
Can I use MotoMix in a gasoline-only four-stroke engine?
No. Use the fuel specified in that engine’s manual.
Can I use MotoMix in a battery chainsaw?
No. Battery equipment does not use engine fuel.
Can I use MotoMix if my manual specifies another ratio?
Do not assume it is suitable. Follow the manual’s fuel and ratio instructions.
Can I pour MotoMix into the bar-oil tank?
No. Use approved bar-and-chain oil in the oil tank. Fuel does not replace chain lubricant.
Should I adjust the carburetor after switching to MotoMix?
Not just because of the fuel change. If the saw runs abnormally, follow its service instructions or seek qualified help.
What should I check before starting after refueling?
Check that the cap is secure, there are no leaks, the chain brake is engaged, and the bar and chain are clear. Move away from the fueling point before starting.
What is the fastest safe check before I leave?
Match the model’s manual to the fuel label, confirm the premix ratio, and do not add oil to MotoMix. Then check leaks, chain tension, and bar-oil delivery.
(This article was written by one of our staff writers, David Hensley. Visit our Meet the Team page.)
