Why Cooling Your Engine Before Shutting It Off Does More Harm Than Good

For generations, experienced drivers have sworn by a simple ritual. After a long highway drive or a spirited run on mountain roads, you do not simply turn off the engine and walk away. You let the car idle for two, three, or even five minutes. The theory seems plausible. The engine is hot. The turbocharger is glowing. Letting it run at idle allows oil to circulate, heat to dissipate, and components to cool down gradually rather than suffering thermal shock from an abrupt shutdown. This advice was once excellent. Today, it is not only useless but actively harmful.