What term describes the temperature at which a fuel will ignite when subjected to compression?

• A. Flash point
• B. Auto ignition temperature
• C. Ignition temperature under normal pressure
• D. Specific gravity

Answer: (B)

Auto-ignition temperature is the temperature at which a fuel will ignite due to heat alone, such as the heating from compression, without any external spark or flame. In engines or scenarios where air-fuel mixtures are compressed, the rising temperature from compression can reach this threshold, causing spontaneous ignition. The flash point, by contrast, is the temperature at which vapor can ignite in the presence of an ignition source, not from compression heating. Specific gravity is simply a density-related property and isn’t about ignition. The term “ignition temperature under normal pressure” isn’t the standard reference used for this concept. So the best term for ignition caused by compression heating is auto-ignition temperature.