What is the difference between cold start and hot start in cars?
3 Answers
Car cold start and hot start differences are as follows: Cold start refers to starting the engine when the coolant temperature is low; Hot start means starting the engine when the coolant temperature is high, with the only difference being the temperature of the coolant. Compared to hot start, cold start has the following two disadvantages: 1. Cold start is more harmful to the car: More than 80% of engine wear occurs during the cold start phase. 2. Cold start requires more time to start the vehicle: 1) During cold start, the internal temperature of the engine is too low, making it difficult for the air-fuel mixture to vaporize and combust. 2) During cold start, the engine oil temperature is insufficient, requiring time to increase the oil temperature. 3) During cold start, the gaps between internal engine components are larger, necessitating a warm-up period for thermal expansion to gradually reach the specified clearances, as excessive gaps prevent the oil film from adequately covering and lubricating the parts.
A cold start refers to when the car has been parked for a long time and the engine has completely cooled down before ignition. At this point, the engine oil has solidified and become sticky, so the oil pump takes some time to push it up and lubricate all parts of the engine. That's why the car may rumble loudly for a few seconds before stabilizing during startup, consuming more fuel, especially noticeable in winter, and prone to shaking. On the other hand, a hot start is when the car is restarted shortly after being driven, with the engine still warm. The oil flows smoothly like water, so the engine typically starts immediately upon turning the key, with a gentle and smooth sound, and it's more fuel-efficient. I often notice that cold starts cause more wear and tear on the engine over time, leading to increased carbon buildup. Regular checks on the engine oil and battery are necessary. The difference can be quite annoying, but installing a preheater can help alleviate some of the issues.
I can immediately tell the difference between cold and warm starts when driving: On cold mornings, the car struggles to start like it's still half-asleep, with the fan whirring loudly and the throttle feeling sluggish. It lacks power for the first two minutes and guzzles fuel. Warm starts, however, are a breeze—like when I return from grabbing coffee, the engine fires right up, and power is instantly responsive, as smooth as a satisfying meal. I think this comes down to the engine's temperature adaptation—cold weather makes it shrink up, while warm weather lets it stretch out. To minimize wear, avoid leaving the car parked too long when cold; it saves fuel, is eco-friendly, and extends engine life. Making it a habit to wait 10 seconds for a quick warm-up before driving does wonders for the engine.
