The 190D is a bit more modern and refined than the '73 you mentioned and the '82-'84 cars you have researched.

The 190D was the first Mercedes-Benz diesel to incorporate their "Engine Encapsulation System", which was essentially a bunch of acoustic padding combined with an engine and tranny undertray which totally contained the drivetrain in a sound absorbing chamber. The motor mounts and tranny mount are also designed to almost completely isolate vibrations from the rest of the chassis.

On the cars which have these parts in good working order, the engines are *very* quiet when the hood is closed, and very little noise or vibration enters the passenger compartment. In fact, it is almost eerie to start the car when the motor/tranny mounts are fresh--it feels like the ignition switch is connected to another vehicle!

Both the 4 and 5 cylinder 190Ds get very good fuel economy, and performance is certainly adequate. From personal experience I can say that engine longevity is most impressive, with only minor problems occuring infrequently.

-BUT-

The '82-'84 SDs are the "real" diesels. Cast iron block and head, no special sound insulation, zillion mile longevity, *decent* fuel economy (not particularly spectacular though), and probably slightly better build quality.

These cars are a good bit larger than the 190, which is fine by me! I'm 6 feet tall and 165 lbs, and I have to max out the seat adjustments (except the recline adjustment) on a 190 just so I can drive it comfortably. I find the interior of the old SDs to fit my tastes more.

It just depends on what you want--lotsa space with decent fuel economy OR a smaller car with kickass fuel economy...

-Joe