Just changed the spark plugs - do the old plugs look OK? The pic below shows
top left = rear rotor, leading (plug is a 7)
top right = rear rotor, trailing (plug is a 9)
bottom left = front rotor, leading (plug is a 7)
bottom right = front rotor, trailing (plug is a 9)
Notes on the pics: the front rotor has that classic tan colour which we\'re taught is a sign of a good mixture. Is this still true for the rotary? The rear plugs are a little blacker (running slightly rich? - a good sign?)
The plug on the top right does not have a chunk missing, some of the carbon on the surface just flaked off!
And they all have a circular wear pattern, presumably where the spark has eroded the 4 outer electrodes - again, is this normal? Plugs are 3k mile old, by the way.
(The car is std (inc ecu), and run on Optimax).