We own a car with 100,000 miles on it and the transmission just went bad. It's going to cost nearly $2,000 to replace it. To buy a new vehicle — a minivan — would require almost $20,000. What do you suggest?

A We recently went through the same situation you describe and found that a good rule of thumb is that the least expensive car you can own is the one that you already have!

Studies by Runzheimer International, a worldwide transportation consultant, consistently show that it is less expensive to operate a car for longer periods of time.

While it's true that repair costs tend to escalate, especially as a car reaches the 100,000-mile mark, these expenses would usually be more than offset by the cost of financing and the immediate depreciation that occurs when you purchase a new car. Most new cars lose 20% of their value as soon as you drive them off the lot.

If you financed $20,000 for a new car at 7% over five years, your monthly payment would be nearly $400. The $2,000 cost of replacing the transmission is the equivalent of five monthly payments, so in essence, you will break even with replacing the transmission if the car lasts at least another five months.

Obviously, you'll want to do much better than just breaking even on this decision, so you'll need to make some estimates as to how much longer you think the car will last.

Is the car in good shape otherwise? Ask your mechanic what his experience is with your particular model. You may find that with a new transmission and a regular maintenance schedule, the car will take you another 50,000 miles without any substantial problems. If this is the case, you'll be miles ahead financially by replacing the transmission.

Two other issues worth taking into consideration are time and safety. There comes a point where a car is in the shop so often that it becomes a true burden from a time standpoint. While it can be difficult to measure this cost in purely economic terms, if the repair history of the car is such that it is making it difficult to fulfill other responsibilities, it's probably time to replace it.

Safety needs to be a primary concern when it comes to family vehicles. If your old car, even with a new transmission, is unreliable in other ways, you'll probably want to replace it. You certainly don't want your wife or children put into a situation where they are stranded because the car consistently breaks down.

While time and safety are certainly valid issues to take into consideration, don't fall into the trap of using them as an excuse to purchase a new car, when the real reason is that you just want to own something new.

After reviewing all of the facts, you'll be in a position to make a good decision for your family.

God love you!

Phil Lenahan is vice president of Catholic Answers.