What happens to specific fuel consumption (SFC) when the temperature decreases?

When the temperature decreases, specific fuel consumption (SFC) decreases because the air density increases, which can enhance engine efficiency. Colder air contains more oxygen molecules per unit volume than warmer air, allowing for a better fuel-to-air mixture in the combustion process. This improved mixture can lead to more complete combustion and greater power output from the engine without necessarily increasing fuel flow. As a result, the engine can operate more efficiently, resulting in a lower specific fuel consumption.

In contrast, the other options suggest various misconceptions about the impact of temperature on fuel efficiency. The notion that SFC increases due to reduced engine efficiency overlooks the benefits of increased air density at lower temperatures. The choice indicating that SFC remains unchanged fails to recognize the relationship between air density and combustion efficiency. Lastly, the idea that SFC decreases due to an increase in fuel viscosity lacks relevance, as the viscosity of fuel affects flow characteristics more than it impacts combustion efficiency directly.