Is it recommended to replace all coils when one is bad or just the bad one? My 2005 545i has 80,000 miles and last summer the plugs/wires were replaced. Thank you.

 

You could take this opportunity to get some new lowering springs if your into that kind of thing

 

Sorry, was referring to ignition coils.

 

Since there is one coil per sparkplug versus the standard configuration of one coil per 8 cylinders, each coil only works 1/8 the amount. My car has 200K on the clock and has never had a coil replaced yet. Knock on wood! YMMV!