After doing all the regular stuff and issues with with w210, problem started with this knock I couldnt chase down after 250000 km only at idle ran great other wise , thought nozzles nope, almost gave up on it , my buddy recommended this stuff( Wynn's tune up in can) drive it for week or two before oil change, hell I dont know why but more Knowlegable people could chime in to the why part ! but she purrs like a kitten now I would like to share this with you! coming from a guy who spent akmost spending $2000 on a problem a $5 dollar can rectified