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40:1 Mix Ratio Calculator & Chart

Quick Answer A 40:1 mix ratio means 40 parts gasoline to 1 part 2-stroke oil. For 1 gallon of gas, you need 3.2 fl oz (95 mL) of oil. This ratio is common ratio for older outboard motors, some trimmers, and vintage equipment.

40:1 Mix Calculator

40:1

Fixed ratio for this calculator

Oil Needed

You Need
3.2
fl oz
for 1 gallon at 40:1 ratio
Milliliters
95
US Fluid Ounces
3.2
Liters
0.095

Need a different ratio? Use our full calculator →

What is a 40:1 Mix Ratio?

A 40:1 mix ratio means you mix 40 parts gasoline with 1 part 2-stroke oil. This creates a fuel mixture that is 2.44% oil and 97.56% gasoline by volume.

The 40:1 ratio is common ratio for older outboard motors, some trimmers, and vintage equipment.

The 40:1 ratio equals approximately 3.2 fl oz (95 mL) of oil per gallon of gasoline, or about 25 mL per liter.

Complete 40:1 Mixing Chart

Use this chart for quick reference when mixing fuel at 40:1 ratio:

US Gallons

Fuel (Gallons) Oil (fl oz) Oil (mL) Oil (Liters)
1 gallon 3.2 fl oz 95 mL 0.095 L
2 gallons 6.4 fl oz 190 mL 0.190 L
2.5 gallons 8.0 fl oz 238 mL 0.237 L
3 gallons 9.6 fl oz 285 mL 0.285 L
4 gallons 12.8 fl oz 380 mL 0.380 L
5 gallons 16.0 fl oz 475 mL 0.475 L
6 gallons 19.2 fl oz 570 mL 0.570 L
10 gallons 32.0 fl oz 950 mL 0.950 L

Liters

Fuel (Liters) Oil (mL) Oil (fl oz)
1 liter 25 mL 0.85 fl oz
2 liters 50 mL 1.69 fl oz
5 liters 125 mL 4.23 fl oz
10 liters 250 mL 8.45 fl oz
20 liters 500 mL 16.91 fl oz

Equipment That Uses 40:1 Ratio

The 40:1 ratio is common ratio for older outboard motors, some trimmers, and vintage equipment:

Older Outboard Motors

2-stroke outboards manufactured before 2000, especially from Mercury, Yamaha, and Johnson/Evinrude.

Some String Trimmers

Older model string trimmers and brush cutters from the 1990s and early 2000s.

Vintage Chainsaws

Chainsaws manufactured in the 1990s and earlier.

Older Leaf Blowers

Professional leaf blowers from the 1990s.

Always Use Your Equipment's Recommended Ratio

Using the wrong ratio can damage your engine. Check your owner's manual for the correct ratio.

Compare ratios →

40:1 Ratio FAQs

How much oil for 1 gallon at 40:1?
For 1 gallon of gasoline at 40:1 ratio, you need 3.2 fl oz (95 mL) of 2-stroke oil.
What equipment uses 40:1 ratio?
The 40:1 ratio is common ratio for older outboard motors, some trimmers, and vintage equipment.
Is 40:1 the same as 2.44%?
Yes, a 40:1 ratio equals 2.44% oil by volume. This means 2.44% of your total fuel mixture is 2-stroke oil and 97.56% is gasoline.
How do I mix 40:1 fuel?
To mix 40:1 fuel:
  1. Pour desired amount of gasoline into an approved fuel container
  2. Measure 3.2 fl oz of 2-stroke oil per gallon (use chart above)
  3. Add oil to gasoline (not the other way around)
  4. Cap the container and shake for 30 seconds to mix thoroughly
  5. Use within 30 days for best results
View detailed mixing guide →

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