Buttons tend to be used for 'on/off' functions, such as engaging the pit-lane speed limiter system, while rotary controls govern functions with multiple settings, such as the traction control programme, fuel mixture and even the car's front-to-rear brake bias - all functions the driver might wish to alter to take account of changing conditions during the race. Google
Monitoring oxygen levels in the exhaust is a way of gauging the fuelmixture. Google
COXOC (Co-zoc) is an oxygen- bearing fuel additive that carries an additional 37% pure oxygen into the fuelmixture. Google