Hello, can anyone access any service information on the spark plugs torque spec for GLS450 (the six-cylinder, M256 engine)?
I have changed plugs on any of my vehicles in the past and have generic information about what it could be, but I remember some of the Mercedes had indexing plugs and required the proper torque. I wanted to follow the service specs for those.
Thank you!

did you ever find this or do yourself? i was quoted $1200 to change the plugs at the dealer and as far as i can tell should be a pretty simple swap @ ~$30/plug

When changing your spark plugs yourself, you may run into deteriorated plug wires.
My dealer found them at my 40k checkup and warrantied them.
Too much insistance on biodegradable parts by Germany, IMO.

yes after speaking to a couple of dealers i found one who will do it for $900 and will probably go that route since i'm still under warranty if they happen upon a degraded harness. the guy did say it tended to be more common on the GLS but that it was relatively widespread

23Nm like all German brands.

Indexing is addressed automatically by buying and installing dealer-purchased spark plugs and tightening to 23Nm.

slight update - found a different dealer who will do it for less than $600. i had it in recently for diff/xfer case service and they did a visual on the harness which looked fine (but they said usually it fails when you start removing the wires) so i'm going to wait a few months until i'm almost out of warranty. that way the harness has more time to start looking like crap and if it fails when they replace the plugs it should be covered

Good plan.
My dealer found the wires to be questionable at my 40,000 mile b service, and replaced them at that time, under warranty.

that's helpful to know - i'm at 33k miles so still kind of "early" on the mileage but at 5 years. just don't want to get stuck replacing the harness especially since it's such a known issue and defect

any idea if the new harness is any better than the old one? obviously will just happen again if they haven't changed anything

I have the same question.