So, a couple of weeks ago my father in law mentioned buying a new battery because his was 5 years old (and subzero weather was in the forecast). That got me pondering on the way home as to when I last bought a new battery for my 1990 240. I couldn't remember and looked through my records. The answer was "never." I bought the car in 2001-
9 years and 109,000 miles ago.Huh.
A couple of times it didn't start when it was really cold (-20F or colder) but started later in the day when it got up to -10F. Otherwise no electrical unreliability that I had noticed.
So I went and got a new battery. The old one was an Interstate and, since that one worked out so well, so's the new one. My mechanic put 'er in, tested everything, etc.
Driving home I noticed that the headlights were actually white, not yellow. The car ran better in general. My mileage, which had dropped below 20 mpg in the cold weather has bounced back to 22 or so. It starts with many fewer revolutions. The windshield wipers move faster. Etc.
So- my imagination? Or is my notion that the battery does nothing but supply energy to start the car outdated?