What's the Best $500 You Can Spend on Your Car?

So you just came into a little money—$500, to be precise. Lucky you! Why not spend it on your car?

You won't be able to get a set of custom rims or tires for that kind of scratch, but you can still make five bills go pretty far when it comes to tricking out your car or truck. Here are some ideas.

WeatherTech floor mats ($84.99 to $124.99)

There's ordinary floor mats and then there's WeatherTech. WeatherTech's floor mats are engineered and laser-cut for specific vehicles and are designed to channel mud, sand, slush, and water away from your vehicle's carpeting and protect your interior in even the nastiest weather. They're made from a tough-but-flexible, rubberlike compound and designed to last for years.

Performance air filter (Around $50)

Your engine runs on air, fuel, and spark, and any time you can enhance one of those three factors, you can squeeze a bit more performance out of it. Air filters used to use a pleated-paper medium, but the latest generation uses a cloth filter material that can trap particles down to a couple of microns in size with minimal restriction in airflow. It can mean a noticeable bump in performance and fuel economy, and the best part is that it's not even a bolt-on item—you just locate the air filter box, undo a couple of snaps, drop the new filter in, and you're on your way.

Window tint ($20 or less for DIY, $150 or so for custom)

A window tint does more than make your car look sharp from the outside. It helps preserve your upholstery, dashboard, and carpets from the sun's punishing UV rays, and it keeps the car noticeably cooler and helps the A/C do its job a bit better.

Dashboard mat ($40 to $50)

A faux-suede dashboard mat complements the original look of your vehicle and protects the dashboard against drying and cracking from the sun's rays. It's fastened with hook-and-loop fasteners to make sure it stays secure and helps make your car's interior a little more inviting.

Seat covers ($20 and up)

Whether you've got a car, truck, SUV, or minivan with cloth, leather, or vinyl upholstery, seat covers protect your seats and help express your style and personality. Choose from a huge selection of styles at prices that are surprisingly affordable.

Tow hitch (Around $150)

Adding a tow hitch can be tricky, since it needs to be solidly attached to the frame and mounting specifics can vary from one vehicle to the next. You will probably want to add trailer brake and light connections, as well, meaning that unless you're pretty confident about such things you might be better off leaving tow hitch and receiver hitch installation to a pro.

Truck accessories 

If you've got a truck (like so many of us do), there's everything from a handy bungee storage net ($19.95) to a receiver hitch kit ($69 and up), running boards and nerf bars ($179 and up), grille guards and bull bars ($195 and up). Best part is that accessories like this don't just look cool, they're practical and useful on a truck.

While it's true that $500 doesn't go as far as it used to (neither does $5,000, for that matter), it might go a lot farther than you think. And unless you're buying a vehicle from a trusted seller, complete with service records, it might be a good idea to take any cash you have left over and invest in a radiator flush and transmission flush. Did you know you can test the condition of your coolant with a refractometer? The hygrometer was the standard way of testing coolant for years, but a refractometer is more exact.

NOTE: check with a mechanic before doing a transmission flush. Many techs and service advisers now recommend not performing this service on a high-mileage vehicle, as it could dislodge varnish and other deposits in the transmission without flushing them out and could lead to trouble.