50:1 vs 25:1 Oil Mix Ratio

Whether you are purchasing a new motorcycle or looking at a large array of power equipment such as chainsaws and string trimmers, there is a very good chance that the equipment you are buying is run by a 2-Cycle Engine.

Even most outboard motors used in boating are 2-stroke engines. This may come with a host of questions, particularly about the type of gas/oil mixture used to run a 2-Cycle engine.

Today we will be looking at what type of fuel is needed and how to come by it, whether purchasing pre-blended fuels or mixing your own oil and gas mixture.

A 2-Cycle Engine, also known as a 2-stroke engine, runs differently to your conventional 4-stroke engine and therefore requires a special oil mix of fuel used to prevent engine damage and eventual engine failure.

What is a 2-Cycle, 2-Stroke Engine?

It would be good to start by looking at a brief explanation of how a two-cycle engine works and why it needs to run on a gas to oil mix in opposition to just regular unleaded gasoline.  

This air cooled engine is characterized by two piston strokes, meaning, the piston moves up and down twice per crankshaft cycle. Whereas a 4-stroke engine has 4 piston cycles for a total of 2 crankshaft rotations.    

Two-cycle engines are generally lighter than a 4-cycle engine and are usually simpler in design. For this reason, these small engines are optimally designed for use in smaller crafts and tools such as leaf blowers.

2-cycle air-cooled engines require an oil mixture of petrol and 2-stroke oil to run, following a direct mixing ratio. The reason being, gasoline acts as a combustion agent and the oil serves as a lubricant for the engine.

Two-stroke Fuel Ratios Explained

It is vital to get your oil mix ratio right when mixing 2-stroke (or two-cycle) engine fuel, for maximum engine protection and performance.

If the ounces of oil per gallon of gasoline are too high and there is too much oil in your oil mix, the engine will struggle to perform optimal combustion, and it will produce higher smoke emissions.

Too little 2-cycle oil in your gas mixture, and you might sustain engine damage due to overheating and your engine life may be decreased.

Oil mix ratios  and the right amount of 2-cycle engine oil per gallon of gasoline may depend on several things. As a good starting point, check your owner’s manual or your manufacturer’s instructions to be sure of the gas to oil ratio for the machine in question.

Otherwise, the age of the machine, the size of the engine and the specific manufacturer may have varying requirements.

How Much 2-Stroke Engine Oil To Mix per Unit of Gas?

As mentioned before, referring to the owner’s manual or the engine label is the best way to determine the correct oil to gas mixture.

However, the overall rule of thumb is 40:1 for 2-stroke power engines. That is 125 milliliters of 2 stroke oil to 5 liters of gasoline in metric or 3.2 fluid ounces of 2-cycle oil to one gallon of gasoline.

For every additional measurement of gasoline, the ounces of oil need to be adjusted accordingly.

Choosing The Correct 2-Stroke Engine Oil

There are tons of different 2 stroke oils on the market these days, and choosing the correct one may be a daunting task. So there are a few things that can be looked at that may determine why some choices are better than others.

Synthetic oil is great for most 2 stroke fuel systems, as it has a low smoke point and is fairly clean. This will allow for clean burning within the engine and is perfect if you are using your machine every day.

Mineral oil is a cheaper option, but in this case cheaper is definitely not better. Mineral oils tend to be less clean and could leave residue or build up in your combustion engines. This will sooner or later require more maintenance and cleaning and will ultimately show a minor difference in performance.  

Of all the current manufacturers making oil for your 2-stroke cycle engine, it’s good to pick a refined 2 stroke oil that is not too cheap and preferably synthetic with a low smoke point.

This will make sure that your equipment engines stay in a good and clean working condition. Only requires some light maintenance from time to time.

It is also possible to buy pre – blended fuels, if you are short on time and need to get your hands on 1 fuel mix quickly. Just be sure to check the shelf life.

How To Make 2 Stroke Fuel?

  1. Always use a storage container that has been specifically designed for gasoline storage. A 5 liter water bottle would be a poor choice. Make sure you are using a jerry can or any other gasoline safe container.  
  2. Determine the ideal fuel oil mixture  by checking the handbook or manual. The correct mixing ratio is very important, too much oil or too little will not be good.
  3. Add half the amount of unleaded gasoline to your container, add the  2 stroke oil to your gasoline and fill the rest up with the other half of your fresh gasoline.
  4. Shake the container so that the fuel and oil mix properly.

Take a look at the following gas to oil mix ratios to know exactly how many gallons of gasoline need to be mixed with your choice of 2 stroke oil:

Fuel & Oil Mixture Chart – Two-Cycle Engines:  

Mixing RatioOne GallonTwo GallonsFive Gallons
20:16.4 oz.12.8 oz.32 oz.
25:15 oz.10 oz.26 oz.
30:14.3 oz.8.5 oz.21.4 oz.
40:13.2 oz.6.4 oz.16 oz.
45:12.8 oz.5.7 oz.14.2 oz.
50:12.6 oz.5.1 oz.12.8 oz.
60:12.1 oz.4.3 oz.10.7 oz.
80:11.6 oz.3.2 oz.8 oz.

The 25 1 oil mix seems to be the easiest to mix because of the rounding of the amounts.

Is Too Much Oil Harmful to My Equipment?

Not really. If your oil mix ratio contains excess oil, it is likely that the engine will not fire, and you will be left standing with gasoline combined with too much oil. In this case, just an additional one gallon of gas.

If the engine does fire, keeping the revolutions low is advisable to avoid large amounts of smoke, but otherwise you should be able to run your engine like this without damaging it.

However, we always suggest the correct oil mix ratio for the maximum amount of performance. Getting the correct amount of oil and gas mixed is best.  

Using the Correct Unleaded Fuel To Mix

The correct type of unleaded fuel in your gas tank is extremely important for a well running 2-Cycle air – cooled engine.

There are several choices of fuel, but when making your selection, make sure that the ethanol content is not more than ten percent, and it has a minimum octane rating.

By doing this, you will avoid too much moisture building up in your tank as ethanol attracts moisture when exposed to the air.

Immediately there will be a noticeable difference in performance as the oil mixes with water and it’s properties change. This will then require a full engine cleaning.

If this goes unnoticed, you will eventually have to pay for additional repairs on your product engine, which is what you want to avoid.

Tips for Mixing 2 Cycle Oil

  • If you are unsure about whether it is a two-stroke oil mix, just have a look at the color. Two-cycle motor oil is dyed either green or blue, so the oil mix will always be characterized by this color. This does not help in determining the oil ratio, however.  
  • You should never keep two-stroke oil with fuel mix for longer than a month unless you have mixed in a fuel stabilizer additive that will prolong the life of the two-cycle gas.
  • Make sure that your container or Jerry can is spotlessly clean inside and around the cap. to avoid dirt from ending up in your tank.
  • Draining your equipment of any oil mix before storing it for longer periods of time is advisable. Let your engine run completely dry to make sure all the oil mix has been burned.
  • Never run a 2-stroke engine on regular gas only. Running traditional two-stroke motors without the required ounces of oil, will leave the engine unlubricated and this will cause damage. Only a 4-cycle engine can run on clean gasoline.

Conclusion of 50:1 vs 25:1 Oil Mix

Be sure to use at least the correct amount of oil in your mixture. Using too much oil by a small percentage of oil will not cause harm to your two cycle engine, but not using enough two cycle oil can cause severe damage to your engine. So you could use a 25:1 oil mix in place of a 50:1 mixture, but not the other way around.