Played Straight: Bob's car is old and rusty, tops out at 40 mph, and does not always start right away.
Exaggerated: All of the above, with the caveat that the car must be started using some non-conventional means, originally came from a country that no longer exists due to civil war, economic collapse, or a brutal invasion from a neighboring country, and has more duct tape than paint on it. It also breaks down about once a week, has been on 60 Minutes more times than it's been on the road, uses ridiculous amounts of gas, has been mistaken for abandoned and/or stolen from a junkyard more times than it's been on the road, and was once disqualified from a Soapbox Derby race for lack of structural integrity.
Justified: Bob is too cheap or poor to buy a Cool Car (or even a halfway decent one).
Bob is purchasing the car as part of an experiment, in which the car doesn't really need to move.
Bob is purchasing parts or scrap metal, not a whole car.
Bob is homeless and needs a car (no matter how much of a clunker it is) to live in rather than to drive around in.
Subverted: What a Piece of Junk: Bob's car may look like crap, but it actually works really well.
Double Subverted: ...But there have been times when it's lived up to its reputation as an Alleged Car.
Deconstructed: The car appears more affordable than it is; spending all that money on repairs causes it to be a ripoff. And let's not even mention the safety concerns.
Reconstructed: Bob finds a really good body shop, and they make the car like new again.
Parodied: The car has an Embarrassing Nickname, which everyone in town knows from local newspapers, TV news, and YouTube videos.
Not even the local junkyard will take in Bob's car for scrap.
The car is shaped suspiciously like a lemon with wheels. Square wheels. With patches on them.
Lampshaded: "Wow, what a hunk of junk!"
Zig Zagged: Sometimes Bob's car runs poorly, sometimes it runs well.
Averted: Bob's car is neither an Alleged Car nor a Cool Car, but it's very good at getting from point "A" to point "B" (and points "C" through "Z" on special occasions)
Invoked: Bob sees an ad in the paper for a used car priced at just $500, and thinks it's a good deal.
Defied: Bob decides to save his money for a car that's good-quality, because he knows that it's a better investment in the long run. Even though it sucks not having a car now.
Discussed: "How can that piece of shit even run?"
Conversed: "I dunno. I think Bob should just sell it for scrap."
Played For Laughs: Almost always is.
Played For Drama: The car is dangerous, has cost him thousands in repairs, and is a threat to his physical and mental health.