Nanotubes signal when engine oil needs changing

A new, easy-to-fabricate sensor made from carbon nanotubes detects when automobile-engine oil needs replacement.

As a car is driven, its lubricating oil undergoes chemical reactions with air and with combustion by-products. Those reactions degrade the oil—for instance, by causing chemicals known as hydroperoxides to build up. In previous work, other researchers had observed that carbon nanotubes become more electrically conductive when exposed to hydroperoxides.