If thieves don't want it, you shouldn't have it.
One of the coolest things about being an automotive enthusiast is that the cars most people see as only an appliance are objects that we can form bonds with. We carefully select our first cars and make sure we got the best bang for our buck. Performance, age, looks, cult appeal, these are all aspects we consider before we plunk down the cash on our latest road partner. Then, through abrasive driving habits or poor maintenance, the car wears down until it's barley drivable. Here is how you can tell if you need to refresh the wheels sitting in your driveway.
Having the check engine light on is akin to hearing a toddler say "uh oh," because nobody knows how grave the problem is. It could just be that the poor girl peed herself or maybe she flushed the car keys down the toilet. Either way, the check engine light is the car's way of saying that something is wrong, and just like you wouldn't neglect the troubled toddler, you shouldn't neglect a check engine light. Even if you know what the problem is, it's a sign of things to come if you let the dashboard have a chronic case of Christmas tree lighting. Those who leave the check engine light on for extended periods of time risk having other problems pop up and not finding out about them until it's too late.
Once you take the car to a mechanic to get the check engine light sorted (or fix it yourself, whatever floats your boat and wallet), it's important to take the costs of the repairs as well as the type of fixes done into account. Are the problems fairly common signs of healthy aging or are they signs of imminent death? Replacing dusty air filters and worn out shocks are completely different procedures than rebuilding a transmission or installing a new crankshaft. If many of your car's recent repairs are due to lack of prior maintenance or even misuse, it may be time for a new car. As a rule of thumb, if the repair costs more than the car is worth, ditch it and get a new one because it may end up saving you money in the long run.
Not everyone wants a car that announces itself and its occupants' insecurities as well as a Lamborghini Aventador Roadster, but it is nice to have a car that looks somewhat presentable. Most cars meet this criterion with varying degrees of success, but it's the true clunkers that fail miserably and make all passengers feel a bit embarrassed to be riding in a jalopy. A good way to test out how badly you need a new car is to take it to a bad part of town and leave the doors unlocked. If it's gone the next morning, then you didn't need a new car (although ironically enough, you're going to get one). If the car is still in the same place you left it, buy a new car. In short, if your car is visibly worn out to the point that not even thieves want it, it's time for a new ride.
Our needs are constantly changing in life, and unless the things around us adapt too, we'll be stuck with more chores than necessary. Given that many of today's cities are auto centric and most rural areas require some form of transportation of long distance hauls, our cars are more than just appliances. They are companions that weather the storms and the sunny days of life. That's why a used 90s Mazda Miata that you bought fresh out of college might be impractical a few years later when your girlfriend says she wants to have a talk while an empty pregnancy test box sits on the counter. Luckily, automakers have tried to greatly expand the variety of cars that exist to suit any palate of needs. Take your pick.
It's always a bad sign when your car starts to play music even though it's lacked a working sound system for the last three years. It's common to hear the occasional creak or rattle, but when driving your car requires earplugs from the constant chatter of lose ailing parts and strained metal, it's time to say goodbye. The wider the range of noises, the sooner an automotive replacement should come in. Usually the suspension is the first to start talking followed by loose interior components. The brakes and chassis are next, followed by the death rattle of a shorn transmission or an engine that's about to seize. Do your ears and your old car a favor and let it go into a happy retirement once the noises are loud enough to disturb a conversation.