<<Not sure what the official capacity is - I think it was changed. If you put in 7 quarts it will be between the lines on the dipstick.>>
Tom is correct . There is a TSB from Benz on the matter.
The new capacity is now 7 l, down from 7.5 l.
[7.9 qts to 7.4 qts] w/filter.
They recommend Editing all owner manuals as such.
There is also a follow-up TSB that calls for dip stick measurement modification to be Between the marks measure HOT [ normal operating temp]
I have noticed the ceasing of a front seal leak after adjusting to the modified instuctions/capacity, but don't know for sure if they are related , nor have I been able to find out the reasoning for these TSBs.