Thanks for suggestion on brakes. I think they are ok - had them changed about 8 months ago - but I will check em out.

At present you are correct - no engine warning light - however for several months I did have a glow plug code ( replaced them) and one related to the relay. Recently the light went out - so I assume all is okay with electronics ( unless of course the warning system itself now has an issue - but I doubt.)

But yes it seems odd that such a signficant drop in such a short period of time - happened after I brought it to a mercedes dealer for change in front end bushings.