As an expert in the field of fuel chemistry and thermodynamics, it is important to understand the various factors that can affect the freezing point of unleaded fuel. The freezing point of fuel is a critical parameter for its performance, especially in cold climates where temperatures can drop significantly.

Unleaded gasoline is a complex mixture of hydrocarbons, the main component of which is octane. The freezing point of pure octane is around -40°C (-40°F), but the actual freezing point of gasoline can be influenced by several factors, including the presence of additives, ethanol, and other components in the fuel blend.

Ethanol is a common additive in gasoline, especially in blends marketed as E10, E15, or higher. Ethanol has a lower freezing point than octane, which can lower the overall freezing point of the gasoline blend. The freezing point of ethanol is around -114°C (-173°F), so when it is mixed with gasoline, it can reduce the freezing point of the mixture.

Additives are also used in gasoline to improve its performance and stability. Some of these additives can affect the freezing point of the fuel. For example, pour point depressants are added to lower the temperature at which the fuel becomes too viscous to flow.

Temperature is a crucial factor in the performance of gasoline. While the freezing point of pure octane is around -40°C, the actual freezing point of gasoline can be higher due to the mixture of different hydrocarbons and additives. In colder climates, winter-blend gasoline is formulated to have a lower freezing point to ensure that it remains liquid and can be used in engines even in extreme cold.

The statement that gasoline with ethanol will freeze lower is generally correct. However, the specific freezing point can vary based on the ethanol content and other components in the fuel. For northern-state winter blend gas, it is reasonable to assume that the fuel has been formulated to withstand temperatures as low as -70°F (-57°C), which is well below the freezing point of pure octane. This is done to ensure that the fuel remains usable in the harsh winter conditions of those regions.

It is also important to note that the ability of a gasoline engine to start is not solely dependent on the freezing point of the fuel. While the freezing point is a critical parameter, the engine's ability to vaporize the fuel at low temperatures is equally important. If the fuel does not vaporize properly, the engine will not start, regardless of whether the fuel has actually frozen.

In conclusion, the freezing point of unleaded fuel is influenced by the composition of the fuel, including the presence of ethanol and additives. While the freezing point of pure octane is around -40°C, the actual freezing point of gasoline can be lower due to these factors. Winter-blend gasoline is designed to have a lower freezing point to ensure performance in cold climates. However, the ability of an engine to start is dependent on the fuel's ability to vaporize, not just its freezing point.

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Gas with ethanol will freeze lower. I would hazard a guess that for northern-state winter blend gas, going down to -70F (the freezing temperature of octane) is fine. Of course, that's probably all moot. Gasoline engines don't start when they get too cold, because the fuel doesn't vaporize properly.read more >>