The 40:1 ratio is used by many string trimmers, older equipment, and some marine engines. Mix 3.2 fl oz of oil per gallon of fuel for proper lubrication.
Quick Reference
Gallons
Liters
Fuel (Gallons)
Oil (fl oz)
1 gallon
3.2 fl oz
2 gallons
6.4 fl oz
2.5 gallons
8 fl oz
3 gallons
9.6 fl oz
5 gallons
16 fl oz
10 gallons
32 fl oz
Also see
50:1
32:1
25:1
24:1
20:1
16:1
100:1
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Facts About 40:1
⛽
PER GALLON
3.2 fl oz
🧪
PER LITER
25 mL
📐
OIL PERCENTAGE
2.4%
Equipment Rated for 40:1
This equipment uses a 40:1 mix ratio. Always check your owner's manual to confirm.
Ryobi
Poulan
Craftsman
Weed Eater
Troy-Bilt
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⚠️
Ethanol Hazard
Use E0 when available, or E10 if your manual allows it. Higher-ethanol blends absorb water faster, age poorly, and can damage small-engine fuel systems.
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Use the calculator to get exact fuel and oil amounts.