Is It Bad to Drive Long Distances and Turn Off the Engine Immediately?

Driving long distances can be a fun and relaxing way to explore new places and enjoy the scenery. However, it can also put a lot of stress on your engine, especially if you have a turbocharged vehicle.

Driving long distances can be an enjoyable and rewarding experience, but it can also put a lot of stress on your engine, especially if you have a turbocharged vehicle. You might wonder if it is bad to drive long distances like 250 km and turn off the engine immediately. The answer is: it depends!

The Effects of Turbocharging

A turbocharger is a device that increases the power and efficiency of an engine by forcing more air into the combustion chamber. A turbocharger consists of a turbine and a compressor that are connected by a shaft. The turbine is driven by the exhaust gas from the engine, and the compressor draws in ambient air and compresses it before it enters the intake manifold. This results in a higher air density and more oxygen, which allows more fuel to be burned and more power to be generated.

However, turbochargers also have some drawbacks, such as higher cost, complexity, and heat generation. Turbochargers run very hot due to the high pressure and temperature of the exhaust gas and the compression of the intake air. If a turbocharged engine is shut down immediately after a long drive or a high load, the oil that lubricates the turbocharger can "cook" or clog in the oil passages, leading to damage or failure of the turbocharger. This is one of the greatest problems with turbochargers and can be prevented by using modern intercoolers or aftercoolers.

The Importance of Cooling Down

To prevent oil degradation and turbocharger damage, it is recommended to let the turbocharged engine idle for a few minutes or drive gently for a while before shutting it down, allowing the oil to circulate and cool down the turbocharger. This is especially important for older or less efficient turbochargers, which may not have adequate cooling systems.

Read Also: Turbocharged Engine Maintenance: Dos and Don’ts

The engine temperature also depends on other factors, such as the ignition timing, the fuel quality, the cooling system, and the ambient temperature. The optimal engine temperature for most internal combustion engines is between 87 and 103 degrees Celsius (or in the range of 195 to 220 degrees Fahrenheit). If the engine temperature is too high or too low, it can affect the engine performance, efficiency, and emissions.

The hottest your engine will get is during the short period of time after you turn it off, this is a condition called "heat soak". During heat soak, your engine is not running so your cooling system is not cooling, and the extreme temperatures that were created inside your engines combustion chamber that heat is now soaking/spreading to the rest of the engine components, thus when you turn it off the engine gets hotter regardless of the conditions it was being driven under.

Heat soak can affect various engine components, such as the intake air, the oil, and the sensors. Heat soak can reduce the engine performance, efficiency, and reliability, and increase the risk of engine damage. Heat soak can also cause an intermittent no start condition, as some sensors or modules may fail at certain temperatures.

Heat soak can be reduced by using an intercooler or an aftercooler, which are devices that lower the temperature of the intake air before it enters the engine. Cooler air is denser and contains more oxygen, which improves the engine power and fuel economy. Heat soak can also be avoided by driving gently for a few minutes before shutting down the engine, allowing the heat to dissipate and the fluids to circulate.

Read Also: Turbocharger: Troubleshooting Common Problems Associated With The Turbocharger

The Exceptions to Cooling Down

While cooling down is generally recommended for turbocharged engines or engines that have been working hard for a long time, there are some exceptions where cooling down is not necessary or even harmful.

• One exception is when you have a standard non-turbocharged engine that has been running at a steady speed and low RPMs in higher gears. In this case, your engine is relatively unstressed and well-lubricated, and turning it off immediately upon arrival is no worse than doing the same thing in city driving.
• Another exception is when you have a modern turbocharged engine that has an advanced cooling system or an oil cooler radiator. In this case, your turbocharger may not get as hot as older or less efficient models, and your oil may not degrade as easily as conventional oils. Some vehicles may also have an electronic system that keeps the oil flowing even after you turn off the ignition, preventing oil clogging in the turbocharger.
• A third exception is when you have a novel system for reducing engine charge air temperature to below ambient levels. This system is called a turbo-cooling system (TCS), and it uses a turbine and a compressor to expand and compress the intake air, respectively. The TCS reduces the engine charge air temperature by exploiting two thermodynamic effects: the Joule-Thomson effect and the recuperative effect. The TCS has several advantages over conventional intercoolers or aftercoolers, such as higher cooling efficiency, lower weight and volume, lower pressure drop, and lower cost. The TCS can also improve the engine performance, fuel economy, and emissions by increasing the density and oxygen content of the intake air.

Read Also: Why Your Car Is Losing Coolant But No Leak and What Should You Do?

Conclusion

You might wonder if it is bad to drive long distances like 250 km and turn off the engine immediately. The answer is: it depends!

If you have a turbocharged engine or an engine that has been working hard for a long time, it is usually a good idea to let the engine idle for a few minutes or drive gently for a while before shutting it down, allowing the oil to circulate and cool down the turbocharger and the engine. This can prevent oil degradation, turbocharger damage, heat soak, and engine problems.

However, if you have a standard non-turbocharged engine that has been running at a steady speed and low RPMs in higher gears, or if you have a modern turbocharged engine that has an advanced cooling system or an oil cooler radiator, or if you have a novel system for reducing engine charge air temperature to below ambient levels, you may not need to cool down your engine before turning it off. In fact, cooling down your engine may be unnecessary or even harmful in some cases.

Therefore, the best way to know whether you need to cool down your engine or not is to check your owner's manual or consult your mechanic. They can give you specific advice based on your vehicle model, engine type, driving conditions, and maintenance history. By following their recommendations, you can ensure that your engine stays healthy and happy for a long time.

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