Definition
The fuel-to-air ratio that produces the maximum power output from a reciprocating aircraft engine at a given throttle setting. It is slightly richer than the chemically correct (stoichiometric) ratio, typically around 12.5 parts air to 1 part fuel by weight, where the engine develops its highest power but not its best fuel economy.
Plain English
The fuel mixture setting that lets the engine make the most power. It uses a little more fuel than is strictly needed for combustion, because that extra fuel helps the engine produce its strongest pull.
Context Anchor
Seen in piston-engine operations when leaning the mixture for takeoff, climb, cruise, or performance checks.
Derivation
The name is descriptive: the mixture setting that gives the 'best power.' It contrasts directly with 'best-economy mixture,' which is leaner and gives the best fuel mileage rather than the most power.
Why Pilots Care
It maximizes available engine power for critical phases such as takeoff and climb while keeping temperatures and fuel flow within safe limits.
Intuition Check
Best does not mean best for every purpose here. Best-power means best for making power, not best for saving fuel.
Example Sentence 1
During takeoff and climb, the pilot keeps the mixture near best-power to ensure the engine delivers full rated horsepower.
Example Sentence 2
In the climb the pilot adjusted to best-power mixture to maintain the highest rate of climb.