Another interesting thread.

Someone already mentioned this but I thought it might be worth examining it again.

The W123 car has the drag coeficient of a car designed before the gas crisis of the early 1970's, probably in excess of .40. Meaning it is pretty poor. If you make an inventory of where the engine's power on any car is going at the factory cited top speed, you will find the greatest bulk of it going to pushing air out of the way. To take a stock 240D engined W123 car to 92 mph would require 14% more power. I am reluctant to believe there are 14% swings in output capacity between cars coming off MB's production line. Maybe plus or minus 2 or 3% total, but not plus or minus 14%, or even plus 14% minus 0%.

However, if someone had a slightly lowered car, maybe undersized tires, aerodynamic hubcaps (not those Bundt cake alloys), no passenger side mirror, Euro headlamps, and got a 2 or 3% reduction in the drag coefficient, they might actually see a higher top speed by a few mph with an engine that was within the normal factory variations, although on the high end of the distribution.

One of the reasons the W126 and especially the W124 cars go to higher top speeds with the same (W126) or a slightly higher performing (W124) engine, is they have much better drag figures. My W210 E300D TurboDiesel feels like it will just keep accelerating past 120 mph. It likely will, but if it were a W123 body, going 120 mph would require over two and a half times the power of the 240D to make that speed. Cars like the W123 280E were capable of those speeds, but had engines that could pump out 185 horsepower. The W124 with that horsepower went nearly 145 mph.

The point is, a slight advantage in drag coefficient, like skinny tires and smooth hubcaps and so on, might get you the extra few mph that are being discussed. I think they will before I would believe someone has a stock 240D that has the output of a stock non-turbo 300D. So, Benz240D probably did see near 92 mph, but not just because his engine is so good. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)