Ok,
In episode 61, "The Smelly Car", JS is driving at least a 5 or 7 series BMW. In other episodes, he drive a SAAB convertible. The point is really that as far back as ep 61, JS is sporting quallity wheels.
But in the Cadillac Part 1&2, Elaine's interest is reignited once JS annouces he's buying Morty a Cadillac. Elaine says she didn't realize Jerry was doing so well.
So, is it because he's buying the Caddy for Morty ? Or, was Elaine jsut asleep at the wheel when the BMW sedan stunk ?
C. Parker