You started to see smog equipment in '75 but initially not everyone used catalytic converters. Some, like BMW and Mazda, used thermal reactors. Leaded fuel wa

You started to see smog equipment in '75 but initially not everyone used catalytic converters. Some, like BMW and Mazda, used thermal reactors. Leaded fuel was common enough that part of the smog check was to ensure that a leaded nozzle couldn't fit.