Boiling down my purchase decisions…. There are SO many cars to choose from in the Southern California area, and I want to make an informed decision.

It’s likely going to be an early turbodiesel, but what year? – I'd like to know if there were any significant engine differences between the earliest turbo diesels (early 80s) and the ones built later, such as the 1983-1985 engines? (I'm not looking at anything newer than the 1985 cars.)

Are they pretty much the same, or were the later ones better built (beefier internals?) or have better ancillaries such as injection pumps, cooling capacities, turbos, etc., etc..

Secondly, are the turbos just as reliable as the normally aspirated cars – in other words, should I look at earlier cars (pre-turbo) assuming that they accelerate quickly enough to satisfy my needs?

Thanks again everyone for your help! MUCH appreciated!

The engine you are looking for is the 617.950,.951, and .952. These are the 3.0 5 cyl. turbo diesel engines Mercedes used from '78-'85. The internals of the turbo diesels are different from the non-turbo diesels since there is more horsepower to be handled. For the turbo'd engines, Mercedes desgined oil jets that spray a percise stream of oil up into the piston to cool them off. I don't believe they put these in the non-turbo'd engines. There is 45% more horsepower in the turbo'd engines. The horsepower rating for the non-turbo engine is something like 90 bhp. Whereas the turbo is rated at 120.
The cars that had these engines were the W116 300SD '78-'80, W123 300D,300CD,300TD '82-'85, and the W126 300SD '81-'85.

Many opinions on this I expect but what I read indicates that the turbo version gets better milage (sounds like oxymoron doesn't it but there is some complex mechanical logic) and is reliable (turbo can last life of engine). So....given the increase in power, decision is an easy one.

Anyone know of reason(s) not to have the turbo version?

It is true the turbo'd engine gets better fuel economy. Also the reason the turbos last is due to the fact that diesel exhaust is not as hot as a gasoline eng. Now, why is the exhaust cooler?, I don't know. I am still on the learning curve with diesel engines.

I would never buy another non turbo Diesel engine unless it was in a tractor. More power with same or better milage is the reason.

P E H

Yea Turbo
 

In going from my 84 volvo diesel to my 84 300DT, I'm reminded of my journey from the bicycle to the motorcycle.

pass a line of cars and feel that turbo working, nothing better except maybe a big salmon on light tackle.
William Rogers........