Question about changing spark plugs.
 

Are the change intervals based on time or mileage?

Car is a 2010 (owned it since new) but only has 21k miles.

Stealership is telling me that they should be replaced...?

Dealer is trying to rip you off

What's new? And 90% of people are unsuspecting and go along with their "advice."

The plugs are recommended to be changed at 100K miles. There are always exceptions to that guideline, but I wouldn’t think at 21K miles they would need to be changed. Pull a plug or two and see what they look like.

Ask your husband to take care of it

Which leads to my 2nd question as Ive never changed plugs before.

:(

The entire process seems pretty easy.

But unsure about the amount of "torque" needed to tighten.

From the videos Ive been watching, people will hand tighten until snug and then apply an additional quarter turn with the wrench.

Sound about right?

11 foot pounds is the spec.

approximate feel value would be hand tight.............

cylinder heads are aluminum and you do NOT want to over-torque them and possibly make removal impossible due to damaged threads

This is what has me a bit worried about doing it myself.

:(

Should I disconnect the battery before attempting to remove the plugs?

And add a dab of Anti-Seize compound to the spark plug threads before threading the spark
plugs into the cylinder head.

Should the battery be disconnected?

no need

With 21,000 miles on your plugs ... your wasting your money by changing them

Plugs
 

Yes it is always a good idea to disconnect the battery in most cases. Your 1/4 turn would be more for the rocker arms. Just make them hand tight and then snug them down a bit if you don’t have a torc rench. Not that big of a deal. I would do as others have said, pull one or two and if they look good then no need to change. Now if you are adding headers and pulling them anyway then I would change them out.

THIS!!! Waste of time and money at 21,000 miles. Forget what they said and drive your car. GM says 100,000 miles for spark plug change.

I should have clarified, this is for a 2010 Mercedes GL550 not my C6.

But I would imagine that its still overkill to change them at 21kmi even though these engines are POS.

Will pull one as suggested, just worried about re-seating it properly.

drive it for another 80,000 miles then start worrying about it .... you are fine just as everybody else has told you so unless you have a "miss or it's running bad leave it alone :thumbs:

Dave

The mileage is definitely not an issue. But let us not forget that sometimes old father time doesn't do us any favors when it comes to getting those little B!@#$%#S out. Probably unlikely that one would have a problem getting them out at 6 years or so, and probably not a problem for longer than that. Even anti-seize could lose its properties after years. But after they've been in there 8 - 10 years I would think why not replace them, for no other reason then to be sure they ain't stuck....LOL.....:flag:

I thought of that before responding - I did my 07's plugs this summer for this reason alone - the car only had 75k miles at the time - I was relieved that they came out effortlessly so I think the OP should be okay

Go on a Mercedes forum and ask.