While we often do our best to keep our cars on the road, both for sentimental and financial value, sometimes you have to recognize when it's time to move on. If you think your ride may be on its last legs, here are a few things to keep in mind.

The basic formula
It's time for an introductory lesson in economics. If money out exceeds money in, it's probably time to sell. This is the golden rule when it comes to deciding whether your car is a fixer-upper or a trader-inner. According to Edmunds, determine if the repairs will cost you more than your car's market value, or compare it against one year of monthly payments. If fixing it up is more costly than either of these, it may be time to say your goodbyes.

As with any advice, this is intended to be more of a guideline than anything etched in stone, but for drivers who are truly on the fence, it can serve as a helpful point from which to evaluate options. Some people may be reluctant to trade in their car. If you're one of them, it helps to know what you can expect financially.

Repair costs can be exponential
You may feel it's cheaper to repair problems with your car than it is to trade it in and buy a new one, and in many cases this is true. After all, spending a couple hundred bucks on a new part – or even a couple thousand for more in-depth repairs – is better on paper than spending substantially more for a whole new car.

However, the older your car is, the more likely it is that you'll encounter maintenance issues on a semi​-regular basis. Every make and model is different when it comes to reliability, of course, but in general, a 10-year-old model won't run as smoothly as a 3-year-old one. Even if small repairs are cheaper, they can add up over time and nickel-and-dime you to death.

The longer you keep your car, the less it's worth
Depreciation is an unpleasant reality of car ownership, but it's still something to keep in mind. Cars lose value exponentially, so the longer you hang on to it, the less you'll get in trade. In fact, keeping your car for five years instead of three can result in an 18 percent loss of value, according to Edmunds. Smart drivers should decide if saving money now is worth the hit they'll take when they do trade in later.

If you're shopping for a used car, head to NJ State Auto Auction. There are hundreds of Carfax-certified cars on the lot, and an in-house finance team available to help get you approved for a loan.