What is carburetor heat used for and when should it be used?

• A. To heat the engine oil to prevent freezing; use when cold temps.
• B. To melt ice in the carburetor by warming intake air; use when icing conditions are suspected.
• C. To melt ice in the carburetor by warming intake air; use when icing conditions are suspected or engine power drops.
• D. To increase engine power by warming intake air; use during cruise.

Answer: (C)

Carburetor heat is used to prevent and melt ice that can form inside the carburetor by routing warmed air into the intake. Ice can develop in the venturi area when moist air is drawn in at conditions near freezing, causing a disruption in the fuel-air mixture and a drop in engine power. By supplying heated air from around the exhaust, carburetor heat melts that ice and restores proper airflow and mixture.

You should apply carburetor heat whenever icing conditions are suspected or you notice a drop in engine power (or rough running) that suggests carb ice. Keep in mind that heated air is less dense, so there may be a slight temporary decrease in performance when you switch it on, but once the ice clears you can switch back to normal airflow. It’s not about heating engine oil or increasing power during cruise; its purpose is anti-icing to maintain steady power.