Actually, they would think otherwise.

"It's amazing how the MB marque gives many the impression of wealth, as most neophytes cannot distinguish the price point of an 18-yr old W126 from an 07 S500...to them they are ALL Mercedes!

I still get nods for my ailling 300E..."

In my experience, as with almost ever decision like this, it depends. It depends on the sales or service scenario. Are the customers always new or infrequent sales calls? Are the visits to the same customers over and over? Are you calling on the boss or underlings? Etc. Etc.

It also depends on whether said old MB is a nice one or a junky looking one.
In my traveling adventures, self-employed consultant, I have driven ''90 300E, '92 300E Sportline, and now '97 S320. You are correct that most people are impressed. I take pains to explain that the cars are old and cheap. Sales psychology varies depending on the audience.

Of course, I don't have the choice of a free company car. Actually, way back in the '80's when the employee owned vehicle program begain at my corporation, I was the maverick.
I happened upon a '79 300CD with 50K for sale by a friend. Believe me, I took major flack from management, co-workers, and customers. They got over it and I was happy in a very safey , butt friendly car.

Steve

Steve