There is a thriving used auto-parts market. In this market, Japanese Domestic Market (JDM) engines have gained a reputation as reliable quality products that meet the needs of car owners. Professionals and experts in the field understand the differences between JDM engines and used engines acquired from other countries. The key advantage that JDM engines have over other used engines is the quality of treatment these engines receive from their Japanese car owners, which allows these engines to remain operational and also retain their integrity. So, what makes JDM engines more reliable than used car engines sourced from other nations? The answer boils down to four main factors, which are discussed below.

1. Japanese Car Owners Meticulously Maintain their Vehicles

In Japan, car owners are required to subject their vehicles, after their first three years of use, to the bi-annual inspection known as Shaken. The protocol used in Shaken testifies to its stringent nature. These protocols guide the process of Shaken inspection that incorporates the steps described hereafter.

To begin, exterior inspection is done, and the vehicle is inspected for exterior modifications that may alter its exterior dimensions. Also, the inspectors ensure that the vehicle conforms to the strict exterior regulations set by Japanese authorities. Secondly, wheel inspection is done to ensure that the wheels are in-line and can turn properly. Thirdly, speedometer inspection is done to assess the accuracy of the readings provided by the speedometer. This is followed by headlight inspection, which assesses whether the headlights work properly and are properly placed and aligned. Then, brake inspection is done to test whether the brakes work correctly. Afterwards, the exhaust system is inspected and its exhaust noise levels measured; as well as tested for the amounts of hydrocarbons and carbon monoxide emitted. Finally, undercarriage inspection is done and the suspension system is examined.

Cars that fail any of the Shaken inspections must be repaired and then retested before they are declared road-worthy. Therefore, cars with minor defects in their exterior body are declared unsafe, even if their engines are in perfect working conditions; and this explains why most JDM engines are as good as brand new engines.

Japanese car owners take their vehicles for regular maintenance at least once per year, especially during the March-April period when the winter tires need to be replaced with summer tires. In Japan, engine oil is usually changed after every 5,000km, while oil filters are changed after every 10,000km; hence ensuring that the vehicle engines maintain their optimal status.

2. High Maintenance Costs

Vehicle owners must regularly maintain their vehicles so that they can remain road-worthy. The maintenance costs are unusually high due to the numerous inspections, including the mandatory Shaken inspection described above, in addition to automobile tax, mandatory insurance, and the costly park fees in the cities. Therefore, even though cars are relatively cheap in Japan (as compared to Europe and North America), the cumulative total of these maintenance costs are so high that it makes little sense for Japanese vehicle owners to continue maintaining cars that are more than a decade old. This leads to car owners purchasing new vehicles. Their old used car is set up for sale, and if the whole used vehicle cannot be sold at once, the engine can be salvaged and sold as a JDM engine.

3. Good Roads and Quality Pavements

Japan has one of the best roads in the world. These roads, alongside their quality pavement, are regularly maintained to the high standards set by Japanese officials. This ensures that vehicles using Japanese roads rarely suffer suspension problems and their engines are seldom damaged.

4. Efficient Public Transport

Lastly, Japan has the most cost-effective public transport system in the world. Therefore, most Japanese car owners prefer to use public transport during weekdays, while reserving their vehicles for driving during weekends. This means that cars in Japan clock a lower mileage per year as compared to cars in Europe, America, and elsewhere in the world. This explains why JDM engines appear relatively new and function better than other used engines of the same age.