edpare

My 2020 GLC300 has 57,000 miles on the odo. Runs and rolls better than the day I bought it. My SA suggested new plugs and I turned her down. What does M-B say about maximum spark plug age?

DanD.

I believe its at 50K miles.

Jetfuture

yep, 50,000 miles. Real good idea to do the coil packs at 100k, even though MB doesn't call for those EVER to be replaced.

W205C43PFL

True but forgot what was the benefit of doing those at 100K, another forum member mentioned it as well.

sn202020

When I replaced plugs at about 100,000km. Nothing was wrong. I thought i could drive on original plugs for another 100,000km.

For Coils, don't waste money until you see misfire codes. Probably never.

W205C43PFL

I wish I can find that other thread, someone mentioned and it was a very convincing reason/benefit to having the coils changed at 100,000 miles.

DanD.

Im going to replace coils at 60K miles, recently I pulled the plugs to inspect cylinders and coils do look old and tired to me. No missfire.

W205C43PFL

Hmmm might not be a bad idea then.

Camaroguy72

50k miles.

mine looked like they needed it on both cars with the same engine.

the injectors fire multiple times per cycle which wears them earlier. Also, corrosion can be a problem and you don’t want plugs getting stuck and breaking in the head. It’s dissimilar metals with electricity going through - galvanic corrosion will eventually become a problem.

get em changed if you’re keeping the car an extended period of time.

DanD.

I was really tempted to add anti seize lub. But it can impact torque. 4th cylinder has most corrosion vs all others.

Jetfuture

The benefit is that for $162 for 4 Bosch coils from FCP Euro, you will likely never have to worry about them again. Nothing more than cheap insurance for me on an engine that is perhaps worth $15,000. You already have the coils unbolted and nearly out when you do the plug swap as it is. Just good science. But my suggestion won't matter, 98% will just wait until they fail and misfire their engine - and that is their choice.

mikapen

"Stuck in the head" is probably the biggest danger of waiting 100,000 mi.

There is an awful lot of threaded portion between the combustion chamber and the sealing surface outside. Pretty impossible to keep it sparkling clean forever.

W205C43PFL

That is a good benefit.