I don't think I really ever heard that saying. So it doesn't mean much to me. Not even changing the car name does it any good for me.

I've heard it used to ways...

1. meaning top of the line
2. meaning to run really fast ex: he was "cadillacing" (used mostly in football)

Cadillac is top of the line, the best, American made...

A friend had a Cadillac Eldorado that she cherished so much she only drove it to the dumpster and back. The dumpster was two miles away and her mechanic recommended she drive it at least ten miles a week to keep everything from locking up. She eventually totalled it in a freak accident after fifteen years of ownership. It was in pristine condition until that point.