If you’re thinking about buying spark plugs online, you might want to reconsider as an investigation has found that 60% of them are counterfeit.

Conducted by Australia’s Federal Chamber of Automotive Industries (FCAI) and a “coalition of automotive manufacturers,” the investigation found that a majority of the hundreds of spark plugs they purchased online were “verified frauds.”

Even more alarmingly, they’re virtually indistinguishable from ‘real’ spark plugs. Many looked perfectly fine and even came marked and packaged with Honda, Nissan, Mazda and Toyota branding. As FCAI Chief Executive Tony Weber said, “We have experts examining the packaging and spark plugs, and even they can barely tell the difference. You won’t know it’s a fake, until it’s too late.”

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Genuine spark plug on left, counterfeit on right

While the spark plugs look legitimate, they use low quality materials and have “inferior construction.” This can best been seen when the spark plugs are cut in half but, sometimes even then, it can be hard to tell them apart.

Unsurprisingly, ‘fake’ spark plugs can hamper performance and potentially damage your engine. According to FCAI, their low quality can cause poor ignition, poor fuel economy and poor engine start ups. They can also overheat and cause a “major drop in engine power, particularly under heavy acceleration or load.” If they continue to overheat, the spark plugs can melt and cause extreme engine damage.

The organization didn’t name the websites where the counterfeit spark plugs were purchased, but said the “automotive industry is working with relevant online trading platforms to remove listings and ban sellers of the illegal counterfeits from their sites.” Of course, the best way to protect yourself from fake parts is to buy from dealers, auto parts stores or legitimate online retailers.