I have to agree with this...I just bought a 1986 300e of my mother's
best friend. Her mother, who is elderly, purchased the car and 1986
and rarely drove it. I only has 24,000 miles on it. Fortunatley they
were always careful in starting the car and running it so it did not
sit for any long periods of time.
When I picked up the car, it idled rough and the engine vibrated alot.
I think that my mom's friend, well intentioned, filled the car up
regular unleaded thinking she was giving me a full tank of gas with my
purchase. To be on the safe side I took the regular out and filled the
car up with premium gas and had an oil change. I also drove it to my
parents house which is about 60 miles away, all highway driving. The
car idles as smooth as can be, you could probably balance a nickel on
edge on the hood while it is in park.