Street-Spotted: Mercedes-Benz 300D Sedan

Mercedes-Benz Diesel W123s never die—as the saying goes. They just go into hibernation until the next gas crisis arrives.

Mercedes' diesel lineup actually kicked off before the W123 arrived. The W114/W115 generation offered a diesel model, and so did earlier generations like the Ponton.

The W123 diesel range at its debut offered the previous-gen 2.4-liter, badged as the 240D, but the 300D quickly arrived with a 3.0-liter inline-five underhood with Bosch mechanical fuel injection. This did not make the 300D a track weapon overnight, arriving with 77 hp and 115 lb-ft of torque on tap in 1977, but later models gained quite a bit of power as the Malaise era dragged on.

"The 300D is meanwhile as sharply different from other sedans as it is from other diesels," Mercedes-Benz said at the time. "One factor is a suspension design that would seem entirely at home in a sophisticated sports car: In making this a performance automobile, Mercedes-Benz engineers took 'performance' to mean not only power in a straight line but stability in curves and adhesion even on rough roads."

It also arrived with the mandatory round sealed beams in place of the rectangular European headlights and more generous bumpers, as the DOT knew you'd be bumping into other things in traffic on a weekly basis. (Dammit, how did they know?)

The round sealed beams on the W123 have grown on us, we have to admit, certainly more so than similar setups on other cars like the Peugeot 505 or the Audi 5000 of the late 1970s. Those two are worth a look if you want to recall how bizarre some cars looked with those headlights back then.

But the W123 never gained the rectangular sealed beams that the Volvo 240 received after trying on the round specs, for instance, as entertaining as that would be to imagine today. (We are getting queasy just picturing that).

The W123 was by no means the sole European diesel sedan available back in the day. The likes of Volvo and Peugeot had their own diesel models, with Peugeot 504s and 505 even serving in New York's taxi fleets for a time, while Detroit dabbled in diesels with far less success.

Smaller offerings like the VW Rabbit also helped make the Malaise era somewhat tolerable, offering a 50% bump in fuel economy over the gas version, though they are definitely not around today.

Out of everything that was diesel in the late 1970s and early 1980s, the W123s appear to be the sole model that survived into the present time in any real number. It's also the car many probably think of when they hear "old Mercedes diesel."

You could start shopping for one today, in 2024, and see lots of W123s for sale within a few hours of your location, and test-drive a couple within a week. That's not something we can say for its competitors from that time.

Finding a diesel Volvo 240 or 740, for instance, is a tall order these days. And Volkswagen Dasher/Passet diesels from that era are.... not well represented in used car listings—let's put it that way.

The time to get a diesel W123 on the cheap probably passed about a decade ago. There is now a small cottage industry aimed at finding and restoring these machines, and flipping them for a tidy profit. In near-concours condition W123s can command over $30,000, so it's easy to see why finding the cleanest ones in the country has paid off for restorers and enthusiasts alike.

Will W123s still be as easy to spot on the street in 2034 as they are today?

We are betting on it, and not just because we have to keep the Street-Spotted series going and well-stocked with W123s.