http://densoheavyduty.com/oxygen-af-sensors/oxygen-sensors DENSO First Time Fit® oxygen sensors are coated with a special formulation of aluminum oxide to trap impurities outside of the ceramic element. In head-to-head testing against the leading competitors, DENSO oxygen sensors were rated two times more resistant to silicone and lead poisoning. At DENSO, we bring together everything we know as an OE supplier to provide aftermarket oxygen sensors that truly are Better By Design™. And while I hate to bring it up, the race engines guys swear by them. Their biggest tip was that the O2 sensor should not be put into place when tuning a leaded fuel motor until the mixture was close. Putting an O2 sensor into an exhaust that was rich would kill it, so dial it in close, then add O2 and finish the mapping. This was a common tip, and guys said the O2 sensors lasted years. I think this is a valid concern vs the shade tree guys just starting a random motor then say 'muh O2 senor died'