What Is a Ratio Rite Fuel Mixer? (Mixing Chart)
A Ratio Rite fuel mixer is a graduated cup used to measure two-stroke oil for premix fuel. Choose the engine maker’s gasoline-to-oil ratio, check that the cup has the matching marks, and measure for your fuel volume. The chart below shows common conversions. It does not replace your equipment manual or apply to every engine.
If the ratio is unclear, don’t guess: the wrong mix can harm an engine. The main task is simple once you know the required ratio: measure the right amount of two-stroke oil, add it to the right amount of gasoline, and mix them in an approved fuel container.
What Is a Ratio Rite Fuel Mixer?
A Ratio Rite fuel mixer is a measuring cup with markings that help you measure oil for two-stroke gasoline. “Ratio Rite” is the product name; the cup does not mix fuel by itself or choose the correct ratio for your machine. Your equipment manual sets that requirement.
The cup is useful because small oil amounts can be hard to measure with ordinary kitchen tools. Depending on the model, its scale may show fuel volume, oil volume, and ratio markings. The printed scales and supported ratios can vary, so check your cup rather than assuming every model is marked the same way.
A Ratio Rite cup is intended for premix engines only when its markings match the fuel volume and ratio you need. It is not a universal fuel-measuring device. In particular, it does not measure bar-and-chain oil or set a carburetor.
When I explain fuel mixing, I start with the manual, not the cup. The manual tells you what the engine needs; the cup helps you measure it. Keep those roles separate, and the process is easier to check.
Measuring the Correct Two-Stroke Fuel Ratio
A two-stroke fuel ratio states how many parts of gasoline go with one part of oil. For example, 50:1 means 50 parts gasoline to 1 part oil. Use the ratio specified for your exact equipment, and treat the figures below as conversions, not advice to change that specification.
Common premix conversions
These amounts use US gallons and liters of gasoline. The metric figures are oil per 1 liter of gasoline; the US figures are oil per 1 US gallon of gasoline.
| Gasoline-to-oil ratio | Two-stroke oil per 1 US gal gasoline | Two-stroke oil per 1 L gasoline |
|---|---|---|
| 50:1 | 2.6 US fl oz | 20 mL |
| 40:1 | 3.2 US fl oz | 25 mL |
| 32:1 | 4.0 US fl oz | 31.25 mL |
| 25:1 | 5.12 US fl oz | 40 mL |
A fuel ratio describes gasoline compared with oil, not oil compared with the finished blend. For practical mixing, use the matching line on your cup for the amount of gasoline you have. If the cup scale and the manual seem to conflict, stop and confirm which units and fuel volume each refers to before measuring.
For example, if your manual calls for 40:1 and you are measuring one US gallon of gasoline, the conversion is 3.2 US fluid ounces of oil. If you have one liter of gasoline, the corresponding amount is 25 milliliters. These examples do not mean your machine should use 40:1.
Check the cup before measuring
First, find the ratio and fuel type in the equipment manual. Then check the cup for the same ratio, the correct fuel volume, and the units you plan to use. A mark for one gallon is not the same as a mark for one liter.
Read the scale at eye level so you can see the oil level against the marking. If the cup lacks the needed ratio or fuel-volume mark, use a suitable measuring tool with clear units instead. Do not estimate from a nearby line.
Ratio Rite Setup and Fuel-Mixing Safety
Good mixing starts before you open the oil bottle. Check the manual for the required ratio and permitted gasoline, then prepare a clean, fuel-compatible container outdoors and away from ignition sources. Wear eye and hand protection, and keep fuel away from heat, sparks, and open flames.
Use this sequence:
- Confirm the instructions. Find the required ratio and permitted gasoline in the equipment manual or fuel label. Do not assume that two machines of the same type use the same ratio.
- Check your tools. Make sure the Ratio Rite scale matches the required ratio and the amount of gasoline. Use a clean, fuel-compatible container.
- Measure the oil. Pour the specified two-stroke oil into the cup and read the level at eye height. Measure the gasoline separately.
- Combine and mix. Add the measured oil to the gasoline in the approved container, close it, and mix thoroughly. Label the blend with its ratio and date.
- Refuel safely. Stop the engine and let it cool before refueling. Wipe up spills before starting, then operate the machine as its manual directs.
Do not pour two-stroke premix into a four-stroke engine. Do not use bar-and-chain oil as two-stroke engine oil; it serves a different purpose. A Ratio Rite measures premix only.
Worked Fuel-Mixing Examples
These examples show how to use the conversions without guessing at a machine’s requirements. They are calculation scenarios, not recommendations for a particular chainsaw, trimmer, or blower. In each case, the equipment manual must specify the ratio shown before you use it.
| Scenario | Manual’s stated ratio | Gasoline measured | Oil amount from conversion |
|---|---|---|---|
| A small batch measured in metric units | 50:1 | 1 L | 20 mL |
| A US-gallon batch | 40:1 | 1 US gal | 3.2 US fl oz |
| A metric batch | 32:1 | 1 L | 31.25 mL |
| A US-gallon batch | 25:1 | 1 US gal | 5.12 US fl oz |
For the first example, check that the cup has a 50:1 marking that applies to one liter of gasoline. Measure 20 milliliters of oil, add it to the liter of gasoline in your fuel container, seal the container, and mix well.
For the second example, the cup must support 40:1 for one US gallon. Measure 3.2 US fluid ounces of oil. If your cup uses a different unit or its marks do not line up with that volume, use another suitable measuring method rather than trying to adapt the scale by eye.
Equipment Operation, Maintenance, and Fuel-System Care
Correctly measured fuel still needs to be handled as the equipment maker directs. Use the required mix only in a premix two-stroke engine, keep the container closed when it is not in use, and refuel with the engine stopped and cool. Clean the cup and equipment as their manuals specify.
An incorrect or poorly mixed ratio can reduce the engine’s lubrication. Too little oil may contribute to piston or cylinder damage, including seizure. Too much oil can also cause smoke, deposits, and poor running. These risks are why the correct ratio matters; they are not a reason to adjust the mix without the manufacturer’s direction.
If you are unsure what fuel is in a container, or whether the ratio is correct, do not start the machine. Verify the mix from its label or prepare a fresh batch according to the manual. If the required ratio is uncertain, check with the equipment maker before operating.
Fuel Storage and Seasonal Preparation
Fuel storage directions depend on the equipment maker, fuel, and container. Follow the machine manual and the fuel product’s label for storage and remaining-fuel guidance. Label premix with its ratio and date so you can identify it later, and keep it in a suitable closed container.
After use, stop the engine and let it cool before cleaning or handling nearby parts. Clean the measuring cup as its instructions allow, and manage leftover fuel according to the equipment maker’s guidance. Do not rely on a remembered age or appearance to decide whether stored fuel is suitable.
Before seasonal use, check the manual for instructions on fuel left in the tank or container. There is no single storage rule that applies to every machine and fuel. If the directions are missing or unclear, contact the manufacturer rather than guessing.
Conclusion and FAQ
A Ratio Rite cup helps measure two-stroke oil, but it cannot tell you what ratio your engine needs. Read the manual first, confirm the cup’s units and markings, and use the matching conversion. If any part of the fuel type, ratio, or measurement is uncertain, pause and verify it before starting the engine.
What does 50:1 mean?
It means 50 parts gasoline to 1 part oil. For the common US and metric volumes shown here, that is about 2.6 US fluid ounces of oil per US gallon of gasoline, or 20 milliliters per liter.
How much oil goes into one gallon of gasoline at 40:1?
Use 3.2 US fluid ounces of two-stroke oil for one US gallon of gasoline, if 40:1 is the ratio specified for your equipment.
Can I use a Ratio Rite cup for any two-stroke machine?
Only if the machine uses premix and the cup’s markings match the required ratio and fuel volume. Check the machine manual and the cup scale.
Does every chainsaw use 50:1?
No. Fuel ratios vary by equipment and engine. Use the ratio in the manual for your exact machine.
Can I use this cup to measure bar-and-chain oil?
A Ratio Rite fuel mixer is for measuring premix ingredients. Use the chainsaw’s instructions and suitable measuring method for bar-and-chain oil.
Can I put two-stroke premix in a four-stroke engine?
No. Do not use two-stroke premix in a four-stroke engine. Follow that engine’s manual for its fuel requirements.
What if my cup does not show the required ratio?
Do not estimate from a nearby mark. Use another suitable measuring tool with clear units, or confirm the correct method with the equipment maker.
What if I do not know the required ratio?
Do not start the machine. Check the equipment manual or contact the manufacturer to confirm the correct ratio and permitted gasoline.
Should I measure oil for a liter of finished fuel or a liter of gasoline?
The chart’s metric amounts are for one liter of gasoline. Check the cup markings and manual so you use the same basis and units.
Does a Ratio Rite cup mix the fuel?
No. It measures oil. Add the measured oil and gasoline to a suitable container, close it, and mix thoroughly.
(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)
