Key takeaways
- The amount you finance is the price, minus your down payment and trade-in equity, plus sales tax and any fees you roll in.
- Stretching from 60 to 84 months drops the payment but costs $3,599 more interest in our example, and longer loans usually carry higher rates.
- Negative equity on a trade-in doesn’t disappear. It’s added to your new loan.
- “Cash rebate or 0% APR?” has a real answer. Compare the total cost of both.
A car loan is a simple amortizing loan: fixed rate, fixed payment, fixed term. The complexity is all in the deal around it, meaning trade-ins, taxes, fees, and promotions. Understanding how those flow into the loan is how you avoid overpaying.
What you actually finance
Take a $35,000 car with $3,000 down, a trade-in worth $5,000 with $2,000 still owed on it, 6.5% sales tax, and $500 in title, registration, and doc fees rolled into the loan:
| Vehicle price | $35,000 |
| − Down payment | $3,000 |
| − Trade-in equity ($5,000 value − $2,000 owed) | $3,000 |
| + Sales tax (6.5% of $30,000) | $1,950 |
| + Fees | $500 |
| Amount financed | $31,450 |
In most states, sales tax applies to the price after the trade-in value is subtracted, which is why the tax here is on $30,000 rather than $35,000. That tax break is one reason trading in can beat selling privately, even at a slightly lower price.
How term and rate change the cost
Here’s that $31,450 financed over different terms. Lenders typically charge more for longer loans, so the 72- and 84-month rows use a higher rate:
| Term | APR | Monthly payment | Total interest |
|---|---|---|---|
| 36 months | 6.5% | $963.91 | $3,251 |
| 48 months | 6.5% | $745.84 | $4,350 |
| 60 months | 6.5% | $615.36 | $5,471 |
| 72 months | 7.5% | $543.77 | $7,702 |
| 84 months | 7.5% | $482.39 | $9,071 |
Going from 60 to 84 months saves $133 a month but costs $3,599 more over the loan. There’s a subtler cost too: cars lose value fastest in the first few years, so on a long loan you can owe more than the car is worth for years. That’s a problem if it’s totaled or you need to sell. For more on the trade-off, see how loan term affects total interest.
Negative equity: the rollover trap
If you owed $9,000 on a trade-in worth $5,000, the $4,000 gap would be added to the new loan. The amount financed jumps from $31,450 to $38,450, and you start the new loan owing far more than the new car is worth.
Options if you’re underwater:
- Keep the current car longer and pay the loan down until you have equity.
- Pay the difference in cash at trade-in instead of financing it.
- Choose a less expensive car so the total loan stays reasonable.
- If you must roll it over, keep the new term short and consider GAP insurance, which covers the gap between the loan balance and the car’s value if it’s totaled.
Cash rebate or low APR?
Manufacturers often offer a choice: cash back, or promotional financing like 0% to 3.9% APR. You can’t have both. Compare the total you’ll pay the lender:
| Offer | Take the rebate | Take the low APR | Better deal |
|---|---|---|---|
| $2,500 rebate or 1.9% APR, 60 months | $566.44/mo at 6.5% | $549.87/mo at 1.9% | the low APR, by $994 |
| $4,000 rebate or 3.9% APR, 60 months | $537.09/mo at 6.5% | $577.78/mo at 3.9% | the rebate, by $2,441 |
The bigger the rebate and the smaller the rate gap, the more the rebate wins. The rate you’d get elsewhere matters too, which is another reason to arrive with a preapproval. The auto loan calculator has a rebate-vs-APR comparison built in.
Getting a better deal
- Get preapproved by your bank or a credit union before visiting the dealer.
- Negotiate the price first, then the trade-in, then the financing. Mixing them lets costs hide in the monthly payment.
- Focus on the total cost, not the payment. “What monthly payment are you looking for?” is how long terms get sold.
- Question add-ons like extended warranties, paint protection, and service contracts. They’re optional, negotiable, and add interest if financed.
- Read the contract for the APR, amount financed, and total of payments, which the Truth in Lending disclosure must show.
Already have a car loan with a high rate? See is refinancing an auto loan worth it?