When buying Denso spark note on the packaging that is to have immaculate design. Lettering and graphics should be clear and is not on the bends. After visual external inspection, open the packing and take the candle out. Look to the Central electrode, which must have a clear cylindrical shape and be mounted exactly in the center. If these conditions are not met, you will likely a fake.
Also a symptom of substandard products is poor treatment of the electrode surface, the presence of saravasti and other defects. The side electrode should also have a smooth location. Nut terminal at the fake products are very easy to remove. Test the strength of attachment of a rod and the insulator, and the surface of the rim, which must have proper form.
Remember that brilliant contact pin is a sign of the "phony" part. Pay special attention to the labeling, which should be bright and clear. Try to scrape it with your fingernail - if you got it, then here is another fake.
Ceramic insulator from the original part has no visible defects, while the forgery can be detected visible air bubbles, which will adversely affect the heat dissipation. The plug electrode has a bright copper color and has an excellent conductivity.
Please note the cost of the candles - often fakes are sold at a price that is significantly below that which establishes an official dealer. Before going to the shop discover online or from the experts estimated the cost of the original product. Always pay close attention to the choice of spark plugs for your car, because of their quality and reliability depends on the life of the vehicle.