Which is better to change plugs... a hot, warm, cool or cold engine? Does it make any difference?

 

I prefer to keep the skin on my hands.



cold is fine.

 

I prefer a warm engine, just started for a minute or two to get the plugs heated up slightly. Metal is softer when it's warm, threaded parts may loosen easier when they are warm as well. Remember, heat is your friend to free a rusty or stuck bolt, apply the same theory to your plugs.

Remember to put antiseize on the new plugs when you put them in place. Don't over torque them either, just snug them up enough to allow the crush washer to collapse. (15 - 20 ft.lbs)