Gasoline Volatility and Seasonal Fuel Blends

Volatility refers to a fuel's ability to change from a liquid to a vapor. This characteristic of fuel is very important in maintaining satisfactory vehicle driveability. If fuel volatility is too low, hard starting and poor warm-up driveability problems may result. If fuel volatility is too high, vapor lock, hot driveability problems, and excessive evaporative emissions may result.

Since fuel vaporization is naturally sensitive to ambient temperature change, refiners typically provide a more volatile fuel blend in the winter to provide easy start-up and cold weather driveability. Conversely, in the summer, a less volatile fuel blend is provided to lessen the chance of vapor lock or hot driveability problems.

Occasional driveability concerns may arise when retailers change blends between seasons (typically spring or fall). For example, if a change was made to a winter blend, yet the weather remained uncharacteristically hot, a hot driveability problem may arise (and vice versa).

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