Motor Expo 2026

While traveling to other provinces, at roadside service stations, it is common to see pickup trucks parked with their engines running. The author once asked a driver and received answers like "The engine is hot, so I can't turn it off, I need to warm it up first," "Why turn it off? I'm leaving soon. Starting it often wastes fuel," and the worst being "I can't turn it off, it might not start again" ?!? How many people truly know why?

Most pickup trucks use almost exclusively diesel turbo engines because they provide good torque, suitable for hauling. If driving fast, the turbo works almost constantly. Upon reaching the destination, the engine should not be turned off immediately, not because the engine is hot, but because the turbo is hot (very hot), for entirely different reasons. As for wasting fuel and not starting, I don't think they are related.

The only reason for this is the "turbo" or the supercharging system itself. The turbo's function is to compress more air into the combustion chamber to increase engine power by recirculating a portion of the exhaust gas from the engine. Whenever the engine is revved at high RPM for extended periods, the exhaust turbine on the outlet side will become extremely hot (if you look at it at night, you might see a faint red glow). Engineers therefore had to design a system where a portion of the engine oil circulates to lubricate and cool the turbo shaft. In some car models, water from the radiator may also be used to assist in cooling (but most cars do not have this).

Consider this: if we turn off the engine immediately, the heat accumulated in the turbo will be extremely high, potentially causing the engine oil remaining in the turbo shaft to burn, because the system is no longer circulating due to the engine being off. In this case, the turbo can certainly be damaged.

However, if we don't turn off the engine immediately and let it idle for about 3-5 minutes (depending on its cooling capacity), waiting for the turbo's temperature to drop before turning it off, no damage will occur. Or, if it is absolutely necessary to turn off the engine and you know you will reach your destination in about 5-10 minutes, reduce your speed and use the highest gear at a constant speed of approximately 60-80 km/h. By the time you reach your destination, the turbo will have cooled down, and you can turn off the engine immediately.

For engines without a turbo, no matter how high the RPM or how long they run, the engine can be turned off immediately because the various cooling systems are already perfectly adequate. Therefore, anyone who knows their car does not have a turbo can turn off the engine immediately, anywhere, anytime. As for cars with a turbo, if driven normally and not too aggressively, they can also be turned off immediately.

Article source autoinfo.co.th