The average new-car monthly payment hit an all-time high of $531 in August 2018, according to Edmunds sales data. It reflects a trend of people preferring costlier SUVs, along with a gradual rise in new-vehicle prices. To cope with the reality of high monthly payments, many people are taking out longer auto loans.

The most common term currently is for 72 months, with an 84-month loan not too far behind. It's been creeping up: 10 years ago, the most common new-car loan term was 60 months, followed closely by 72 months.

Loans for used cars are about as long: The most common term for a used car in 2018 was 72 months. Even though people are financing about $10,000 less for used cars than they do for new cars, it takes them roughly the same amount of time to pay off the loan.

"Consumers are battling two things," said Melinda Zabritski, director of automotive credit at Experian. They are trying to get a good interest rate and a reasonable monthly payment. But a five-year loan often has a monthly payment that is too high for them, and they end up financing for a longer term even if it costs them more down the line, Zabritski said.

Is there any benefit to having a six- or seven-year car loan aside from a lower monthly payment? No. In fact, there are many reasons why you shouldn't choose a long car loan. Edmunds recommends a 60-month auto loan if you can manage it. And here are some reasons why.

Car Fatigue

This is something that many people don't consider before taking out a long loan. We love our cars when they are brand-new, but when the romance fades, we're eager to trade them in for something else.

The average length of ownership for a new car is about 6.5 years (79 months), according to IHS Markit. Used-car ownership averages 5.5 years (66 months). Americans do not tend to drive their cars until the wheels fall off, no matter what they say they're going to do when they buy them.

Let's take those average lengths of ownership and see what happens with various loan terms.

First, new cars: Imagine you have a 72-month auto loan, and you get the itch to buy a new car seven months after paying off your loan, right about at that common 79-month mark. You are only getting seven months without a car payment. If that's the case, you would have been better off leasing two cars in succession, at 36 months each. You would have had lower monthly payments and the enjoyment of two new cars.

If you took out an 84-month loan and you tired of your car at 79 months, you'd be stuck with five more months of paying for a car you couldn't wait to unload. No months are payment-free. If you were really desperate to dump the car, an alternative would be to roll the last five months of the loan into your next car purchase. But that's almost always a bad idea: It creates a longer loan commitment and higher monthly payments for the next car.

Now let's look at used cars: Say you buy a 3-year-old used car and pay for it with a 72-month loan, as most people do. And if you're like most people, you'll be tired of the car after five and a half years. You will still have six months of payments to go.

Even if you can stand another six months with the car (which is now 9 years old), you will not have a single month without a car payment. Again, you might have been better off leasing two new cars back to back. Lease specials can bring some new cars into a price range that's comparable with used cars.

Contrast these situations with buyers who've chosen five-year loans. At the average ownership mark of 79 months, they have already enjoyed nearly two years without car payments and have the freedom to sell the car whenever they want.

Higher Interest Costs

Higher interest rates are another reason to stick with a 60-month loan. The longer the term, the more interest you will have to pay on the loan, both in terms of the rate itself and the finance charges over time. Here's how the numbers look when you compare a 60-month loan to a 72-month loan.

The average amount financed for a new car in 2018 was $31,070, with an average interest rate of 3.2 percent for a 60-month loan. The finance charges over the life of the loan would be $2,593, giving you a monthly payment of $561, which is a considerable chunk of money. It's easy to see why someone would opt for a longer loan.

Contrast that with a 72-month auto loan. The interest rate would be higher, which is common for longer loans, Zabritski said. According to Edmunds data, the rate was about 6.9 percent in 2018.

For our new car with the amount financed of $31,070, the monthly payment for the 72-month loan would be about $528. That seems like an improvement over 60 months, until you see the finance charges: $6,962 over the life of the loan. That's more than two and a half times the interest you'd pay for a 60-month loan.

If you purchased a used car with a 72-month loan, at the average financed price of $21,450, your monthly payment would be $393. It seems like a win from a monthly payment perspective. However, interest rates are higher for used cars, and a rate of 9.6 percent is fairly common. You'd be paying $6,851 in finance charges — almost as much as for a new car.

That extra year spent making payments means it would also take longer to build equity in the car. The faster you get to equity the better.

Negative Equity
A new car typically depreciates about 22 percent in its first year. At the beginning of a car loan, you usually have "negative equity" in the vehicle: You owe more on it than it's worth due to that depreciation. This situation is also known as being "upside down" or "underwater." If you make a down payment that's too small, you put yourself further underwater. And you go deeper still if you opt for a longer loan term. The additional finance charges are to blame.

The time it takes you to build equity in the car varies, depending on what you bought and your down payment. And equity is what you want: It gives you choices. When you have equity in the car, you can sell it if your other bills get out of hand or you lose your job. Negative equity, on the other hand, limits your options if you're in a money bind. It also ties you down if you get tired of your car before it's paid off. A buyer will only pay you what the car is worth, not what you owe on it. You're stuck with the balance of the loan.

Similarly, if you get into an accident and the car is totaled, the insurance company will only pay you what the car is worth at the time of the accident. Unless you have gap insurance or new-car replacement insurance, the remainder of what you owe will have to come out of your pocket.

Lower Resale Value

Resale value is another reason to steer clear of extra-long car loans. If you do plan on selling your vehicle when it is paid off, a 5-year-old car is more desirable and more valuable in the used-car marketplace than one that's 7 years old. A 5-year-old car has lost about 47 percent of its new-car value. A 7-year-old car has depreciated by about 62 percent. Put another way, the new vehicle in our example will be worth roughly $16,479 after five years. It drops to $13,184 at the seven-year mark.

A dealership will likely give you more money for the 5-year-old car. At that age, it's still a great candidate to become a certified pre-owned (CPO) car, which means the dealer will have a more valuable vehicle to sell.

On the other hand, a 7-year-old car is no longer a CPO candidate. Most automakers won't consider a car that's more than 5 years old. Likewise, if it has too many miles, it won't qualify for a CPO program. That means you will get far less for the car as a trade-in.

Alternatives to Long Loans

Let's say you want to buy a new car, but the monthly payments that are being quoted for the usual five-year loan are too high for you. That may be a sign that you're shopping outside of your price range. Take a look at the Edmunds "What Can I Afford?" calculator. You start by entering your ideal monthly payment, and with a few clicks, you'll see cars in your price range.

You also could consider buying a used car. Interest rates are higher for used cars, but since the cars cost less, there's less to finance and the payments will be lower. Just be mindful of the loan terms.

Final Tip

While it's important to know what you can afford in terms of monthly car payments, that shouldn't be your only measurement of a good car loan. Take a look at all the numbers in the sales contract so that you are fully aware of what you are paying for the car.