How does gasoline volatility affect engine starting in cold weather?

Gasoline volatility—a measure of how easily fuel vaporizes—is critical for engine performance, particularly during cold weather. For an engine to start quickly in cold conditions, the gasoline must be sufficiently volatile to vaporize effectively at low temperatures.12

To achieve this, refiners adjust the fuel's composition by adding highly volatile components, such as butane, which has a low boiling point. This process ensures that the fuel system receives the necessary vaporized mixture to ignite properly when the engine is cold.21

However, balancing this property is complex. While high volatility aids cold-weather starting, it can also lead to increased evaporative emissions during refueling and may contribute to vapour lock in hot weather. Consequently, modern gasoline is carefully formulated to account for seasonal and regional variations, ensuring reliable starting while adhering to environmental standards regarding emissions.12