There’s no magic point at which an old car becomes collectible. Age doesn’t translate into value. A 10-year-old Mustang will not automatically be more valuable when it’s 20 years old. A 40-year-old Chevrolet won’t necessarily be more valuable when it turns 50. A wide range of circumstances combine to make an old car an appreciating asset: How many were built, the car’s desirability when it was new, etc.

Four-door sedans rarely become valuable. Cars with four doors are the utilitarian vehicles of the automotive world, usually designed to be more practical than provocative. It almost never pays to hang onto a four-door sedan. They almost always will be regarded as just used cars.
 

Convertibles are the stars. There’s a saying in the collector car game: Interest (and prices) goes up when the top goes down. Convertibles are automotive sex symbols and as we all know, sex sells. If that old car in your garage is a ragtop, you’ve got a possible contender.
 

Options add value. The more extras that were on the car when it was new, the better. A car from the 1960s or ‘50s with power windows and seats was something of a rarity, particularly in a Ford or Chevy. So a 1963 Impala convertible with all the power options would be a keeper.
 

The more power the better. It may not be economically or environmentally appropriate, but an old car with a powerful, optional V8 will almost always bring more money than the same car equipped with the standard V8 or economy six.
 

Originality counts. Collectors pay top dollar for cars that haven’t been modified in any way. To get the most money for a collector car it’s crucial that it still have the original engine and transmission. Rebuilding those components adds value, but the basic parts should be the ones installed at the factory.
 

Never buy a “project’’ car. It’s tempting to look at a cheap old car that’s in need of a complete restoration and think it’s a bargain. Quickly run away from such deals. Unless you’re a master mechanic with too much time on your hands, restoring an old car is almost never economically feasible. Just check the ads that say, “More than $50,000 invested,’’ and the seller is asking $25,000.
 

Buy the best car you can afford. This is really the inverse of the previous tip. While you should avoid restoration projects, you should buy the most perfect car you can. It will retain its value better and need minimal additional investment.
 

Buy a car you love. One of the mistakes people make is they buy a car that they don’t really covet and then become disappointed when they can’t quickly sell it for a big profit. But if you buy a car that you’ve always wanted to own, it doesn’t really matter how quickly you can turn a profit. You’ll be happy to own the car no matter what the market does.
 

Cars are meant to be driven. The tragedy that befalls many old cars - the collectible queens and the aged survivors - is that they sit in garages and are treated like sculptures. Cars are meant to be driven, even if only for a couple of afternoons a month. Driving a well-maintained classic provides a thrill that makes any talk of eventual financial windfall irrelevant.