Most W123s I see out on the freeways here in town travel significantly slower than the flow of traffic, maybe trailing along in the right (or sometimes impeding in the middle or left lane) doing 45-55 at the most. I'm not talking about just diesels, I've passed 230s and 280Es putt-putting down the freeway. I'm usually doing 60-70 and I pass up these putt putt W123s all the time. I talked with an owner once who was driving in from out of town in his W123. He told me it took 4 hours to get to town, I asked "really? was there a bad accident or bad weather or something?" he said "nah, I just drive this car slow." When weather and traffic allow, I usually do that same drive in 2 hrs 45 mins. 
Are you a "putt putt" driver? As for me, nah. I was taught that MBs like exercise. If you putt putt too much, you don't get those carbon deposits cleared out.
Are you a "putt putt" driver? As for me, nah. I was taught that MBs like exercise. If you putt putt too much, you don't get those carbon deposits cleared out.