M.B. Doc...one more question for you, thanks!
 

Hello MB Doc,

Thanks for your reply:

There is a maximum mileage that the system will allow for YOUR driving style. You must have reached that maximum.
That happens if you do a lot of around town driving.
The instrument cluster uses imputs other than oil quality & mileage to calcaluate when the next service is needed

Your answer was in reference to my earlier questions:

The last time I decided to do an oil change between intervals in my C 240, the FSS read "8,000 km A Service". After changing the oil, the FSS automatically extended the mileage by 1,600km reading "9,600 A Service".

I decided to do the same this time by chaging the oil betwen intervals. This time, the FSS read "3,200 km B Service". After the oil change, the FSS still read "3,200 km B Service". This time, the FSS did not extend the mileage after the oil change like it did the last time. I thought it was supposed to extend to a new mileage, but it did not this time around.

I did not understand what do you mean by "maximum mileage". Could you plese eleaborate?

Yes, I did a lot of short trips and stop-and-go driving this time around. It's that why it did not automatically extend the mileage even after new oil has been put into the engine?

Thanks,
Johf

The critera that the instrument cluster uses to calculate the mileage before the next service isn't just based on oil quality.
Load on engine, time, style of driving, & lenght of time that the engine runs. The oil quality sensor can add some distance to the initial 15,000Km, but the total mileage that you can go is related more to driving habits than the quality of the oil.

How does the oil quality sensor work?

I'm very interested to find out.

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