What does "cold start" mean for an engine?

A "cold start" refers specifically to the process of starting an engine when it has not been running for a while and is at ambient or low temperatures. This typically occurs after the vehicle has been off for an extended period, allowing the engine to cool to the ambient temperature.

During a cold start, the engine's oil is also cold and more viscous, which can influence how easily the engine turns over and the efficiency of fuel combustion. Additionally, the fuel mixture may not vaporize as readily, leading to a different starting and running behavior compared to starting a warmed engine. This phenomenon is important for understanding engine performance and maintenance, as starting the engine in colder conditions often requires extra care to ensure optimal functioning.

The other choices involve different scenarios that do not align with the definition of a cold start. Starting the engine while it is warm, after a long drive, or at high RPMs all pertain to conditions where the engine has been running or is operating in a different context than a cold start.