not overfill oil,

just adding oil when needed,

without taking note

LOL! There were mosquito foggers that smoked less than that thing when I first got it! With the other leaks fixed and the head refurbed, it's down to a quart every 1500-2000 miles. I expect that to drop like a stone once the turbo is refurbed (leaking seal on compressor side).

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

If very uniform measurements in all 6 cylinders, I would suspect that all are perfect and your compression testing method is at fault since very unlikely that all would degrade the exact same amount. It is very easy to get wrong compression readings. The adapters must displace exactly the same volume as the parts your removed. If going in the injector holes, this is easy to botch. The gage must have the correct type Schraeder valve at the tip. Some people refurbish with a regular tire one, which has a stronger spring (much dP to open it). Try turning the engine over by hand. If you feel each cylinder resist as a strong "air spring" and you hear each slowly hiss down, you have excellent compression. If you do have low-compression, do a "leak-down" test to find the source. I just apply air pressure to a cyl at TDC (jam crankshaft) and listen for where it hisses (intake = intake valves, exhaust = exhaust valves, crankcase = rings). Haven't done on my diesels, but could probably use the HF compression test adapters to rig to an air hose.

Low compression will not give noticeable power loss. It would make it harder to start on cold mornings. Ditto on check your turbo boost. Run a temp nylon tube from intake into the cabin for a temp boost gage, or even easier secure it under the wipers on the outside. Soot'ed intakes are a problem in diesels and now in the new direct-injection gas engines. That is because there is no fuel spray in the intake to keep it clean and EGR gases bring soot. I read that some manufacturers are moving to adding a small injector at the throttle body of DI engines to keep the intake clean, since owners fuss about the expense of having the intake removed for de-sooting every 50K miles.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Turbo boost is on my dash, showing 12 psi, at load,

at idling I hear the kicking,

timing chain is zero, when checked,

IP is 15 degree, at DTC,

EGR is disconnected,

Oil leak into #1 cylinder is a common 602/3 head gasket failure.

Sixto
98 E320s sedan and wagon

Thank you Sixto,

just drove the car 90 MPH,3700 rpm, for 30 sec,

just to see its capacity,