These days, cars can easily go 200,000 miles or more'”with the proper care and maintenance. Just because you bought your car used doesn't mean you should skimp on its needs. If your car came with the owner's manual (and we sincerely hope you didn't buy a used car that didn't have one) there is a section in it listing what service should be performed at what intervals. These are typically delineated at a certain mileage, or at a certain time.
If your car is four years old with like 24,000 miles on it, you are most likely on a time schedule. If, on the other hand, your car is four years old and has 56,000 miles on it, you're on a mileage schedule. To get a feel for what the previous owner did, check the service records (your car did come with those too, right?).
If the service records aren't available and you have no way of determining what was done when, then your best bet is to try to reset the car's maintenance cycle to zero. At the pre-purchase inspection (please tell us you got one) your mechanic should have taken note of any parts that looked like they were about to fail, if the seller didn't do so, you should replace those right away. Additionally, take a look at your owner's manual and see what service is recommended for the mileage your car is closest to, and have it performed. You'll also want to drain all of the fluids out of the car and have them replaced'”along with the filters that go with them. Similarly, you'll want to check your air filter and make sure it's clean. If it isn't, replace it as well. By replacing all the fluids and filters, you'll know exactly where you are in the life cycle of those vital liquids and can start your own replacement schedule based on this knowledge.
As for the rest of the car, you'll want to spend your first few days with it driving around with the radio off, listening to the car as it does its thing. You want to get familiar with the way it sounds when all is well so if something changes you'll key into it right away. If you followed our guidelines for how to test drive a car, you should already have an idea of the way it sounds when it's running well; you wouldn't have bought a car that sounded like it had problems'”right?
You should also pay attention to the way the car feels when it's going down the road. Different cars have different ride and handling characteristics, get in tune with yours so you'll know right away when your wheels need balancing, or if your brakes or shocks are starting to go bad.
Similarly, you want to keep an eye on the ground or the garage floor beneath where your car is regularly parked. This is the fastest way to spot leaks. Should you spot an unusual puddle, you can get a basic idea of what it is by the way it looks. Yellowish-green, pastel- blue or florescent-orange liquid is a coolant/antifreeze leak and could mean you have a bad hose, water pump, or a leaking radiator. A dark brown, or shiny black puddle is most likely oil. An oil leak is typically the result of a bad seal or gasket. A reddish-pink oily looking spot is likely a transmission or power steering fluid leak. Any of these could lead to very expensive repairs if not treated quickly.
Once you're familiar with the car's rhythms, you'll be able to pick up hiccups quite readily. If you note any unusual sounds, sights or vibrations, get the car looked at as soon as possible. A car is basically a collection of interrelated systems. The failure of one part can have an adverse affect on many others if ignored. Putting off 'minor' repairs will only serve to make the inevitable more expensive. Get in the habit of giving your car what it needs right away if you want to protect yourself from excessive repair costs.
Additionally, a well running car is at its most efficient in terms of fuel consumption. Ignoring repairs can make your car use more fuel, thus saddling you with higher gas/diesel bills. Additionally, if your car has the balance of the factory warranty on it, or you bought an extended service contract, ignoring maintenance can void them and leave you on the hook for repair costs.
In a lot of ways your new used car is like a member of the family. Pay attention to it, get to know it, and if it seems sick, get it treated right away.