But today, you don't need to do that! The idling you do on today's automobile burns valuable fuel and also leaves gas deposit on the cylinder walls that stay with it because the cylinders typically aren't moving as fast as they normally do. This contaminates the engine oil with carbon deposit and also makes your auto's innards unclean.
Idling the car puts pressure on the modern gas injection systems in today's cars. Idling was applied in cool or very hot weathers when gas injection wasn't widespread in older cars. To keep the engine from stalling, people made use of to maintain it running or it could not activate.