50 to One Gas Mixture: Measurements, Chart, and Mixing Instructions

A 50 to one gas mixture contains 50 parts gasoline or petrol to one part two-stroke oil by volume. For one US gallon of gasoline, that equals 2.56 US fluid ounces of oil, normally rounded to 2.6 ounces. In metric units, add 20 milliliters of oil per liter of fuel. This mixture is common in modern chainsaws, string trimmers, leaf blowers, hedge trimmers, and other two-stroke equipment. It is not suitable for every engine, however. Some machines require 40:1, 32:1, 25:1, or another ratio, while oil-injected engines meter their lubricant separately. Always verify the ratio and oil specification in the equipment’s operator’s manual before preparing fuel. Accurate measurement matters because too little oil can cause severe wear, while too much may produce smoke, deposits, and poor performance.

Quick Answer

A 50:1 mixture means 50 parts gasoline to one part two-stroke oil. Use:

• 2.56 US fluid ounces of oil per US gallon
• 2.6 US fluid ounces per gallon when rounded
• 20 milliliters of oil per liter
• 100 milliliters of oil per five liters Only use this ratio if the engine manufacturer specifies 50:1.

What Does a 50:1 Ratio Mean?

The numbers in a fuel-to-oil ratio compare volumes. At 50:1, every 50 equal units of fuel require one equal unit of oil. Those units could be milliliters, fluid ounces, liters, or another volume measurement, provided the same unit is used on both sides of the calculation. For example:

• 50 milliliters of gasoline require 1 milliliter of oil.
• 500 milliliters of gasoline require 10 milliliters of oil.
• 5,000 milliliters of gasoline require 100 milliliters of oil. You do not have to prepare the mixture in 50-ounce batches. The ratio can be scaled to any practical fuel quantity. A 50:1 ratio is commonly described as a 2% two-stroke mix because the oil equals 2% of the gasoline volume: 1 ÷ 50 × 100 = 2% Technically, once the gasoline and oil are combined, there are 51 total parts. Oil represents approximately 1.96% of that completed mixture: 1 ÷ 51 × 100 = 1.96% Both descriptions refer to the same practical 50:1 recipe. In equipment manuals and oil instructions, “2% mix” normally means oil measured at 2% of the fuel volume. This fuel-oil ratio should not be confused with an engine’s air-fuel ratio. The fuel-oil ratio determines lubrication, while the air-fuel ratio describes how air and fuel combine for combustion.

50 to One Gas Mixture Chart

The general formula is: Oil required = fuel volume ÷ 50 Use the same units for fuel and oil during the calculation, then convert the result if needed.

Fuel quantity	Two-stroke oil required at 50:1
0.5 US gallon	1.28 US fl oz
1 US gallon	2.56 US fl oz, commonly rounded to 2.6
2 US gallons	5.12 US fl oz
2.5 US gallons	6.4 US fl oz
3 US gallons	7.68 US fl oz
4 US gallons	10.24 US fl oz
5 US gallons	12.8 US fl oz
1 liter	20 ml
2 liters	40 ml
5 liters	100 ml
10 liters	200 ml
20 liters	400 ml
A premeasured 2.6-ounce oil bottle is convenient for one US gallon. A 6.4-ounce bottle is intended for 2.5 US gallons at 50:1.

One-US-gallon calculation

One US gallon contains 128 US fluid ounces: 128 US fl oz ÷ 50 = 2.56 US fl oz of oil Rounding that result to 2.6 fluid ounces is normal and practical. Do not confuse 2.6 US fluid ounces with 2.6 Imperial fluid ounces because the units are different.

Five-liter calculation

Convert five liters into milliliters: 5 liters = 5,000 ml Then divide by 50: 5,000 ml ÷ 50 = 100 ml of oil This same method works for any quantity. Seven liters, for example, require 140 milliliters because 7,000 divided by 50 equals 140.

US Gallons and Imperial Gallons Are Not the Same

The word “gallon” can cause errors in an international 50:1 fuel mix chart. A US gallon contains approximately 3.785 liters, while an Imperial gallon contains approximately 4.546 liters. Therefore, they do not require the same amount of oil. At 50:1:

• One US gallon requires 75.7 milliliters, or 2.56 US fluid ounces, of oil.
• One Imperial gallon requires approximately 90.9 milliliters, or 3.2 Imperial fluid ounces, of oil. Readers outside the United States may find liters and milliliters easier and less ambiguous. At 50:1, simply use 20 milliliters of oil for every liter of petrol. Also check whether a mixing bottle is marked in US or Imperial fluid ounces. A US fluid ounce is approximately 29.57 milliliters, while an Imperial fluid ounce is approximately 28.41 milliliters.

How to Make a 50 to One Gas Mixture

Prepare premixed fuel in a clean, approved gasoline container rather than trying to blend it casually inside the equipment’s tank. A separate container allows more accurate measurement and thorough mixing.

1. Confirm the required ratio.
   Read the operator’s manual or fuel label. Make sure the engine actually specifies 50:1 and identify the required two-stroke oil standard.
2. Choose a safe location.
   Work outdoors or in a properly ventilated area. Stay away from cigarettes, flames, sparks, heaters, hot engines, and other ignition sources.
3. Use an approved fuel container.
   The can should be clean and free from water, dirt, diesel, stale gasoline, or an unidentified old mixture.
4. Add part of the gasoline.
   Pour roughly half the required amount into the container. This leaves room for the oil to disperse.
5. Measure and add the oil.
   Use a graduated mixing bottle, petroleum-resistant measuring cup, or correctly sized premeasured bottle. Do not estimate by eye.
6. Close and mix the container.
   Secure the cap and agitate the fuel so the oil begins dispersing through the gasoline.
7. Add the remaining gasoline.
   Fill to the intended fuel volume, close the container, and mix it again.
8. Label the container.
   Write “50:1 premix,” the type of oil, and the preparation date on the can. Some manufacturers instruct users to add oil before all the gasoline, while others recommend starting with half the fuel. Follow the model-specific instructions where available. The main requirements are accurate measurement, a suitable container, and complete mixing. Clean the equipment’s fuel-cap area before refueling so debris does not enter the tank. Allow a hot engine to cool, open the cap carefully, and wipe up spills according to local safety requirements.

What Type of Oil Should You Use?

Use two-stroke oil that satisfies the specifications in the engine’s manual. The required formulation depends on the equipment and operating environment. Air-cooled chainsaws, trimmers, and blowers may require classifications such as JASO FD or ISO-L-EGD. Water-cooled marine outboards may specify NMMA TC-W3 oil. A marine lubricant and an air-cooled power-tool oil are not automatically interchangeable simply because both packages say “two-stroke.” Never use these products as premix oil unless the manufacturer explicitly approves them:

• Automotive four-stroke motor oil
• Chainsaw bar-and-chain oil
• Hydraulic fluid
• Gear oil
• An unidentified oil from an unmarked container
• Two-stroke oil that does not meet the required specification Synthetic, semi-synthetic, and mineral two-stroke oils can have different additive packages, smoke characteristics, and applications. The label and engine manual are more useful than assuming that the most expensive formulation is automatically correct. Oil brand does not override the equipment’s specified ratio. A premium oil sold with special instructions should only be used outside the engine manufacturer’s standard ratio when both the oil maker and equipment documentation clearly support that application.

What Equipment Uses a 50:1 Fuel Mixture?

Many modern two-stroke machines use 50:1, including certain:

• Chainsaws
• String trimmers and weed eaters
• Leaf blowers
• Hedge trimmers
• Brush cutters
• Pole saws
• Edgers
• Augers
• Snowblowers
• Small outboard motors
• Dirt bikes and go-karts That list does not mean every model in each category uses the ratio. An older chainsaw may require 32:1, a marine engine may use automatic oil injection, and a dirt bike may have model-specific premix requirements. Look for a ratio printed on the fuel cap, engine label, oil reservoir, or operator’s manual. A separate oil tank may indicate an oil-injection system that does not require manually mixed gasoline during normal operation. Most four-stroke engines keep lubricating oil in a separate crankcase. Adding 50:1 premix to a four-stroke lawn mower, generator, or similar engine can cause deposits and operating problems. Identify the engine type before fueling it. If several machines all specify the same ratio and compatible oil, one labeled fuel can may serve them. If their ratios or oil standards differ, prepare and label separate batches.

40:1 vs. 50:1: Which Contains More Oil?

A lower ratio number means more oil for the same fuel quantity. Therefore, 40:1 contains more oil than 50:1.

Ratio	Oil per US gallon	Oil per liter	Relative oil content
32:1	4.0 US fl oz	31.25 ml	Most oil of these three
40:1	3.2 US fl oz	25 ml	More oil than 50:1
50:1	2.56 US fl oz	20 ml	Least oil of these three
A 40:1 mixture is not the same as 50:1. Using 40:1 in equipment designed for 50:1 adds approximately 25% more oil than specified. Conversely, using 50:1 in an engine requiring 40:1 supplies 20% less oil than its specified amount.
More oil is not automatically safer. Engine design, carburetor calibration, exhaust system, operating temperature, oil quality, and emissions requirements all influence the recommended ratio. Follow the manufacturer’s specification instead of changing it based on a general belief that extra oil always provides more protection.
If a batch has been mixed incorrectly and every input quantity is known, it may be possible to calculate a precise correction. If the existing ratio, fuel volume, oil type, or fuel age is uncertain, replacing the batch is safer than trying to fix it by estimation.

What Happens When the Ratio Is Wrong?

Two-stroke engines depend on oil carried in the gasoline for piston, cylinder, bearing, and crankshaft lubrication. A substantial error in either direction can create problems.

Too much oil

An oil-rich mixture may lead to:

• Heavy blue or gray exhaust smoke
• Oily exhaust residue
• Spark plug fouling
• Carbon deposits
• Restricted exhaust flow
• Hard starting
• Rough idling
• Reduced power These symptoms can also have other causes. A dirty air filter, incorrect carburetor setting, restricted spark arrestor, or weak ignition may produce similar behavior.

Too little oil

An oil-lean mixture can be far more damaging because moving components may not receive adequate lubrication. Possible consequences include:

• Excessive engine temperature
• Piston and cylinder scoring
• Crankshaft or connecting-rod bearing damage
• Reduced compression
• Engine seizure
• Permanent internal damage If straight gasoline was added to a premix-only engine, stop it as soon as safely possible. Do not assume that pouring oil into the tank afterward immediately delivers a correct mixture throughout the fuel line and carburetor. Remove or isolate the incorrect fuel and follow the manufacturer’s recovery procedure. Equipment operated under load without oil may need professional inspection.

Gasoline Quality and Premix Storage

Use fresh gasoline that meets the engine manufacturer’s octane and ethanol requirements. Recommendations differ among brands and regions, so one universal fuel grade cannot be applied to every two-stroke engine. Ethanol-blended fuel can absorb moisture during storage. Heat, air exposure, water contamination, and a poorly sealed container may also reduce fuel quality. Problems can include phase separation, oxidation, deposits, hard starting, and carburetor restrictions. Mix a manageable amount rather than preparing a season’s supply without checking the permitted storage period. Oil manufacturers, equipment brands, fuel stabilizers, and canned premix products may all specify different limits. A stabilizer can slow the deterioration of fresh fuel when used correctly. It cannot restore gasoline that is already stale, water-contaminated, or phase-separated. Store premix:

• In an approved, tightly closed fuel container
• In a cool, ventilated location
• Away from sunlight and ignition sources
• Outside living areas
• Where children cannot access it
• With the ratio and mixing date clearly marked Never pour unwanted premix onto soil, into water, down a drain, or into household garbage. Use an approved fuel-recycling or hazardous-waste service.

Frequently Asked Questions

What does a 50 to one gas mixture mean?

It means 50 equal parts gasoline or petrol are combined with one equal part two-stroke oil by volume. The units can be ounces, milliliters, or another volume measurement, provided the same unit is used for both components.

How much oil goes into one US gallon at 50:1?

One US gallon contains 128 fluid ounces. Dividing 128 by 50 gives 2.56 fluid ounces of oil, normally rounded to 2.6 ounces. A premeasured 2.6-ounce bottle is therefore suitable for one US gallon when the engine specifies 50:1.

How much two-stroke oil is needed per liter?

A 50:1 ratio requires 20 milliliters of oil per liter of petrol. Multiply the number of liters by 20 to find the oil amount in milliliters. For example, six liters require 120 milliliters.

Is 40:1 the same as 50:1?

No. A 40:1 mixture contains 3.2 fluid ounces of oil per US gallon, while 50:1 contains 2.56 fluid ounces. Use the ratio specified for the particular engine rather than treating the two mixtures as interchangeable.

Can 50:1 be used in every two-stroke engine?

No. Some two-stroke engines use 40:1, 32:1, 25:1, or another ratio. Others have automatic oil injection. Check the operator’s manual, fuel cap, or engine label before adding premixed fuel.

Can automotive motor oil be used in a 50:1 mixture?

Ordinary four-stroke automotive oil is not a suitable substitute for two-stroke premix oil. It is not formulated to mix and burn in the same way and may increase deposits, plug fouling, and exhaust restrictions. Use oil carrying the specification required by the engine.

What happens if too much oil is added?

Too much oil may cause smoke, oily exhaust residue, fouled spark plugs, carbon deposits, rough operation, and reduced power. If the amount added is unknown, do not dilute the fuel by guessing. Replace it with an accurately measured batch.

How long can 50:1 premix be stored?

There is no single limit for every fuel and oil combination. Gasoline type, ethanol content, container quality, temperature, stabilizer, and manufacturer instructions all affect storage life. Mix modest quantities, date the container, and follow the shortest applicable storage guidance.

Get the Ratio Right Before You Refuel

Preparing a 50 to one gas mixture is straightforward once the required units are clear: use 2.56 fluid ounces of two-stroke oil per US gallon, or 20 milliliters per liter. The calculation is simple, but compatibility still matters. Before mixing:

1. Identify whether the engine is two-stroke, four-stroke, or oil-injected.
2. Check the manufacturer-specified fuel-to-oil ratio.
3. Select oil that meets the required specification.
4. Choose either US or metric measurements and avoid mixing unit systems.
5. Calculate and measure the oil accurately.
6. Blend and store the fuel in an approved, labeled container. The operator’s manual—not a universal chart—has the final say on the correct ratio and oil type for a particular engine.