Here are the DENSO W16EXR-U11 spark plugs sold by Toyota and DENSO. The ones sold by Toyota are stamped "MADE IN U.S. OF JAPANESE & U.S. PARTS", with the same written on box, and the ones sold by DENSO are stamped "JAPAN", with "Made in Japan" written on box. I am now thinking that the ones sold by Toyota are made by Champion or a similar US spark-plug company, not by DENSO, since the body is machined entirely differently.
There is probably not a significant difference in quality though. It's probably more my trust in Japanese parts and engineering. Until mid-1980s, every Toyota was made in Japan.
There is probably not a significant difference in quality though. It's probably more my trust in Japanese parts and engineering. Until mid-1980s, every Toyota was made in Japan.
