What "genuine" actually means

In the Japanese aftermarket parts trade, "genuine" refers to a part manufactured by the actual brand named on the box: the ignition coil stamped FD Elecman, the timing kit stamped OSK, the valve stamped Dokuro. It ships in factory packaging, carries the manufacturer's own hologram or seal, and traces back through an authorised distribution chain to the factory in Japan. Nothing about it is substituted, repackaged, or made by a third party under license.

For a buyer, genuine is the category where the specification matches exactly what left the original production line, because that is precisely where it came from.

What "OEM" means

OEM stands for Original Equipment Manufacturer, and the term gets used two different ways in the trade, which is where a lot of confusion starts. Some sellers use "OEM" to mean the vehicle manufacturer's own branded part. Others use it to describe a part made by the same factory that supplies the vehicle manufacturer, sold under the component maker's own brand name instead of the car brand's badge.

In practice, an OEM part from an established component brand is usually built to the same specification as the part fitted at the factory, often on the same production line. The difference from "genuine" is mostly about branding and channel, not manufacturing quality, provided the source is authorised.

What "aftermarket" means

Aftermarket parts are made by companies with no direct link to the original component manufacturer. Quality varies enormously across this category. Some aftermarket parts approach OEM tolerances and come from reputable manufacturers. Others cut corners on materials, machining, or testing to hit a lower price point, and that lower tier is also where counterfeit parts hide, often copying the look of a genuine box without the manufacturing behind it.

The word "aftermarket" on its own tells you nothing about quality. It only tells you the part was not made by the original component manufacturer, which means the brand and the seller's reputation matter more here than in any other category.

How to choose the right grade for the job

Not every part on a vehicle carries the same consequence if it under-performs. A few practical guidelines:

  • Safety-critical and high-load parts (brake pads, timing components, ignition parts): genuine or authorised OEM is worth the premium, because failure here is expensive or dangerous.
  • Daily drivers and fleet vehicles: genuine or OEM keeps service intervals predictable and protects resale value.
  • Lower-load parts with a known, reputable aftermarket brand: a good aftermarket option can be a reasonable trade-off on cost.
  • Anything priced far below the going rate for a genuine part: treat that gap as a warning first, not a bargain. It is usually where counterfeits live.

How Jinsen guarantees genuine on every shipment

Jinsen has distributed Japanese aftermarket parts since 1981, including as an authorised Dokuro dealer, and we do not carry grey-market or counterfeit stock. Every shipment that arrives at our Segambut warehouse clears three checks before it is logged into inventory:

  • Sealed packaging: factory seals and carton condition are inspected before any box is opened. Tampered or resealed packaging is rejected on the spot.
  • Unique holograms: each principal brand carries its own hologram, matched against the factory reference before stock is logged.
  • Long-standing supplier partnerships: decades of supplier relationships help Jinsen source authorised Japanese parts from trusted principals and established channels.

If you are buying genuine or authorised OEM Japanese parts, this is the chain of custody worth asking for, whichever distributor you use.