The Powerbuilt brand of 12 point bits set I got at Pep Boys held quite well through my M103 head R&R. I thought my arms would give through the last quarter turn with a 24" breaker bar.

I think it was in the 4/86 issue of Consumer Reports, of all places, that I read that the M103 (300E) has an appetite for oil at revs. They believed it to be by design.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD