50:1 VS 25:1 (Which Oil Mix Is Superior)

Using a proper oil mix ratio is a must. If you mix too much oil, the engine won’t be able to burn gasoline properly. On the contrary, not using oil will wear your engine out. 

So, which oil mixture should you use, 50:1 vs 25:1

50:1 oil mix ratio means 1 drop of oil per 50 drops of gasoline. So, naturally, 25:1 is a thicker mix and it travels slowly. Due to being fast, a 50:1 oil mix is used by current manufacturers. On the contrary, the 25:1 oil mix is very old and only suited for the old engines. 

Anyways, this was only a quick look at the whole discussion. Read along and you may find the information that you’re looking for! 

Understanding The Basics Of Oil To Fuel Ratio

Before jumping into the comparison, first, understand what the oil-to-fuel ratio signifies. This ratio indicates the amount of two-stroke oil that needs to be mixed with a given amount of gasoline to fuel a two-stroke engine effectively.

The numbers ’50’ and ’25’ represent the parts of gasoline in the mix, and the oil quantity is either 1 part in 50 or 1 part in 25, respectively.

The Case for 50:1 Oil Mix


  • Less Smoke and Residue: A higher oil-to-fuel ratio, such as 50:1, generally results in cleaner combustion. This means less smoke and fewer carbon deposits in the engine and exhaust system.
  • Economical Usage: Using less oil in the fuel mixture means you’ll go through less oil over time, resulting in cost savings in the long run.
  • Modern Engine Design: Many modern two-stroke engines are designed to work optimally with leaner oil mixtures like 50:1, as they have better engineering and materials.


  • Lubrication: Some argue that a leaner oil mix might not provide sufficient lubrication for high-performance or older engines, potentially leading to increased wear and tear.
  • Customization: Certain engines might have specific manufacturer recommendations that vary from the standard 50:1 mix, so it’s essential to consult your engine’s manual.

The Case for 25:1 Oil Mix


  • Enhanced Lubrication: A richer oil mix, such as 25:1, can provide extra lubrication, which can be beneficial for engines operating under heavy loads or in high-temperature conditions.
  • Added Cooling: The extra oil in the mix can contribute to better engine cooling, preventing overheating in demanding situations.
  • Older Engines: Some older two-stroke engines were designed to run on richer oil mixtures due to differences in materials and engineering at the time.


  • Smoke and Residue: The higher oil content can lead to more smoke and carbon buildup, potentially affecting exhaust emissions and overall cleanliness.
  • Fuel Efficiency: Richer oil mixes can result in slightly reduced fuel efficiency and more frequent oil changes.

50:1 vs 25:1: Quick Overview

Factors 50:1  25:1 
Engine Type 2 Stroke 2 Stroke.
Lubrication Less  More.
Oil Density Lower Higher.
Viscosity Less More.
Price  Same Same.

50:1 vs 25:1: Detail Comparison

This table only highlights the basics. Therefore, we’ve discussed the comparison in detail:

fuel mixture
Source: Stihlshop.co.nz

Difference 1: Oil Density And Lubrication

A 50:1 oil mix ratio means 50 units of gas for a single unit of oil drop. Likewise, there are 25 units of gas for 1 drop of oil in a 25:1 oil mix. 

So, a 25:1 oil mix is denser. Also, it lubricates better than 50:1. Although that much lubrication isn’t necessary for newer engines. 

Difference 2: Viscosity

Viscosity means the overall flow defiance of a liquid. So, honey has more viscosity than water. Simply put, a mixture of 25:1 gas/oil will have more flow resistance than a 50:1 ratio. 

So, the 50:1 oil mix will move faster. This is a necessity because 2 stroke engines can wear out very fast.

A 2-stroke engine has a very high RPM and needs lubrication as soon as possible. If the oil doesn’t reach in time, the piston will get scratched. 

On the contrary, the viscosity of 25:1 is ideal for older chainsaw models. They need more lubrication and thus the 25:1 ratio provides more than enough. 

Different grades of oils have different viscosity. These numbers are called SAE grades and play an important role in mixing! 

Difference 3: Emissions

Too much oil can’t be burnt properly. 25:1 Oil mix produces more harmful emissions. 50:1 oil mix produces less harmful emissions.

How to Mix 50:1 or 25:1 Oil Ratio? 

We have discussed the advantages and disadvantages of both ratios. But how do I achieve a 50:1 or 25:1 ratio? 

50:1 and 25:1 Ratio Formula: Imperial System 

In the imperial system, you only need to remember two values and calculate accordingly:

  • For a 50:1 ratio, 1 gallon of gasoline needs 2.6 fluid oz of oil
  • For a 25:1 ratio, 1 gallon of gasoline needs 5.2 fluid oz of oil 

Here’s, a small chart in imperial units to help you out:

Gasoline   50:1 Ratio 25:1 Ratio
1 gal 2.6 oz 5.2 oz
2 gal 5.2 oz 10.4 oz
5 gal 13 oz 26 oz
10 gal 26 oz 52 oz

Now you can easily calculate and find out the required oil amount by yourself. However, you can also buy pre-blended fuels and completely ignore this process if you want to. Here are some of my top choices:

No products found.

This will save you time and you can get started right away! 

Making the Right Choice

Now, better lubrication is possible in lesser viscosity thanks to science and technology. Because of them, synthetic oil is now better and it can pretty much lubricate anything! 

So, now older 2-stroke engines can run on a 50:1 oil mix. However, using a 25:1 oil mix will still be the safer option. 

Because manufacturers know their products better than anyone. That’s why you should always use the oil mix which is mentioned in your manual. 

While using 50:1 might have risks, using 25:1 will always be safe. And it’s better to be safe than sorry! 

Frequently Asked Questions

Does 2-stroke oil expire?

Yes, it can expire over time. Usually, sealed 2-stroke oil can go as far as 5 years. However, if opened, they won’t last more than 2 years. Also, when mixed with fuel, you should use the mixture within 2-3 months. 

What fuel is 2 stroke?

There’s no internal oil reservoir in 2-stroke engines. So, the oil mixes with the fuel directly. It works as a lubricant and a fuel at the same time. That’s why when there’s too much oil in the mixture; it causes a smoke emission. 

How long does 2-stroke oil last once open? 

Unlike other oils, 2-stroke oils can expire very quickly. A sealed can or bottle of 2-stroke oil can last up to 5 years. However, it comes down to 2 years after it has been opened. 

Which ratio should I use for my two-stroke engine?

The ideal ratio for a two-stroke engine is typically specified by the manufacturer and can vary depending on the engine model and design. However, a commonly recommended ratio is a mixture of gasoline and two-stroke oil in a 50:1 ratio (50 parts gasoline to 1 part oil).

How often should I change the oil in my two-stroke engine?

Oil change frequency depends on usage and oil quality. Check your engine manual for specific recommendations.

Can I use synthetic oil in both ratios?

Yes, synthetic oil can be used in either ratio, providing improved lubrication and reduced carbon buildup.


And with that, we’re at the end. That was all the information we could provide on 50:1 vs 25:1. We are hopeful that you have found the info that you wanted. 

So, were you able to mix the oil properly? Share your story in the comments! 

Finally, best of luck!

Kevin Smith

3 thoughts on “50:1 VS 25:1 (Which Oil Mix Is Superior)”

  1. The newer 40 / 50 to 1 mixture is solely to make the EPA happy . It is for emissions , not taking the longevity of the engine in consideration at all. I just bought chainsaw direct from China and it takes a 25 to 1 mixture, as they dont care about emissions .

    1. I just ordered a 20″ 58cc Chinese chainsaw for $65. it too says 25:1. can’t wait to compare it to my 25 yr old Poulan (16″ 38cc?) and a used Stihl ms390 (20″ 64cc) that I just picked up. might have to video tape that. 🙂 but for $65 … it only has to last a few years!!

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