Mercedes is pretty clear about the processes and timing for items that relate to Schedule A and Schedule B. I'm not sure why MB chooses to ignore a bunch of items, namely:
- Spark plug replacement
- ATF drain and fill
- Differential gear oil drain and fill
- Steering fluid drain and fill
- Coolant drain and fill
- Engine air cleaner
- Timing belt replacement

Any one know why most of these are not included as scheduled service? For 2023 GLC43 Coupe with TCT and 3.0L V6, what intervals does MB recommend for addressing? Thanks!!!

I don't know of any Mercedes engine that uses timing belts. As far as I know, all Mercedes engines employ timing chains, which should be maintenance-free for at least 250,000 miles.

We just did a service A , 5 years or 50K miles, ( only 29,600 on this 300GLC) and it included spark plugs, engine air filter, engine coolant etc. These are on your list.

I went to the dealer, and this is what I learned for the 43. I suspect 63 probably has some tweaks.

Non-A Non-B Maintenance
Spark plug replacement Every / 50,000 miles or 5 Years
ATF drain and fill with new filter / Every 60,000 miles or 6 Years
Front Differential case drain and fill / Officially sealed for life, but every 60,000 miles or 6 Years is advisable
Rear Differential case drain and fill / Every 30,000 miles or 3 Years
Transfer case drain and fill Every / 50,000 miles or 5 Years
Steering fluid drain and fill N/A – Electronic; no fluid
Engine air filter Every / 50,000 miles or 5 Years
Replace fuel filter Every / 120,000 miles or 12 Years
Coolant drain and fill Every / 120,000 miles or 12 Years
(main circuit and low temperature circuit)

Additional items applicable to the specific models are all part of the A and B services, but there are different A and B services. I forget how many there are, but they are numbered as in A, A1, A2..., B, B1, B2. The service reminder in the instrument cluster will show which one is due. Depending on the number after the A or B additional items are part of the service. So spark plugs for example are part of the 50k/5 year A Service. Don't remember what number that had. This also means that the cost of the different A and B services is not always the same. They all have a different price tag, depending on the items that are part of it. Some dealerships may itemize the service, but it's technically one price for whatever the specific service entails.