benz_addict

I got 80,000KM on my 04 S500 with Service B in 10,000KM left.

I had them looked at by a mechanic he told me couple are so seized up don't think they're firing at all. Can this really happen, if so wouldn't it throw some codes?

Ausmbtech

The std spark plugs on these cars last pretty well with high mileage, they have a service life of 4yrs/120,000kms. I'd just replace them at your next service unless you are having any specific driving problems right now.

Skylaw

You might try a good fuel system cleaner (they are usually more concentrated than fuel injector cleaners). I usually concentrate mine even more by using a full can with only 1/2 tank of gas. Run the car at fairly high rpm (4-5000 rpm) for a few miles of driving (use lower gears). That may clean your plugs.

AH1W-COBRA

4000 to 5000 sustained rpm to clean $150 worth of worn out spark plugs? just replace the plugs and it will clean the combustion process up on it's own.dont use an additive and a $15,000 engine to clean the plugs!.no offense to skylaw,seems like everyone is trying to keep from spending money these days.

AH1W-COBRA

it is possible for old,worn out plugs like yours to errode the center electrode and also to form a deposit bridge on the gap area and prevent an efficient spark.

benz_addict

thanks guys, I will be replacing them and the fuel filter as well

benz_addict

one more question: What's the correct spark gap?

Skylaw

Exactly. And if the bridge is the problem the course I recommended will likely do away with the problem.

Some of those plugs aren't easy to reach.