While still driving my 123 diesel with over 450,000 miles I bought a copy of the "Mercedes - Benz Buyers Guide."
On page 143 and 144 the Summary of the 300E is as follows:
Mercedes-Benz has always built terrific inline sixes and this one is their best. If you can't find what you want in this 3.0 liter gasoloine sedan, try one of its variations, diesel, wagon, Coupe, Convetible, four wheel drive. The market has an excellent supply of well maintained 300 models at a good discount from their orginal prices. A 300E is your best overall buy in a used Mercedes-Benz. Period. End of discussion."
On page 141, there is another interesting two sentences:
"Climate Control problems apply to all post-1980 models, but don't let that put you off. It's just part of the price for the excellence of the rest of the car."
After reading this book in about 1996 while owning a brand new, special ordered 210 car, I began searching high and low for a manual transmission 300E. It took about two years and I finally found one. I wanted it as a toy, but my situation changed and I ended up selling my 210 car. After a time I began using the 300E for my daily driver. My daily drive is 178 miles round trip.
After putting close to 140,000 miles on this $12,000 used car, it is probably the most enjoyable pennies per mile I've ever spent. The most economical pennies per mile has been my 240D.
With this experience under my belt, I TOTALLY agree with the above quotations. Will the car break at one point or another? The answer is Yes, absolutely. ANY car is a machine. Machines eventually have parts that wear out. The difference between this and other cars is what you have while it's running, which will be most all of the time.
My brother-in-law, who happens to be my tech at the MB dealership, and I have an ongoing friendly argument about which is the best car, the 123 or 124. I have at least one example of each, he has only a 124 car. These are both engineering masterpieces IMHO. I always take the side of the 123 car when visiting with him. But, I probably agree with him that the 124 slightly edges out the 123. But, I won't tell him that, after all how can you have an argument when you both agree?
If you drive one of these great automobiles for awhile, properly care for it, and fix it when it breaks, I believe you will understand what I am trying to say.