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What Is an Auto Loan?

An auto loan is a secured loan used to purchase a vehicle, where the car itself serves as collateral. If you fail to make payments, the lender can repossess the vehicle. Auto loans typically have fixed interest rates and fixed monthly payments over a set term, usually ranging from 24 to 84 months. The interest rate you receive depends primarily on your credit score, the loan term, whether the car is new or used, and whether you finance through a bank, credit union, or dealership. Unlike unsecured personal loans, auto loans generally offer lower interest rates because the vehicle reduces the lender's risk.

How Auto Loan Payments Are Calculated

Your monthly payment is calculated using the standard amortization formula: M = P × [r(1+r)^n] / [(1+r)^n – 1], where P is the principal (loan amount), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. The loan amount equals the vehicle price minus your down payment and trade-in value, plus any amount still owed on the trade-in, plus sales tax and fees if you choose to finance them. Each monthly payment splits between interest and principal — early payments are mostly interest, while later payments are mostly principal. This is why making extra payments early in the loan saves the most money.

Frequently Asked Questions

How much should I put down on a car?

Financial experts recommend putting down at least 20% on a new car and 10% on a used car. A larger down payment reduces your monthly payment, total interest paid, and the risk of being underwater on the loan (owing more than the car is worth). If you can't put 20% down, aim for at least 10% and avoid zero-down offers that lead to negative equity from day one.

What's a good interest rate for an auto loan?

As of 2025–2026, good auto loan rates are roughly: 4–6% for new cars with excellent credit (750+), 5–7% for new cars with good credit (700–749), 7–10% for used cars with good credit, and 10–15%+ for fair or poor credit. Rates vary by lender, so always get quotes from at least 3 sources — your bank, a credit union, and the dealership — before signing.

Should I choose a longer loan term for lower payments?

While longer terms (72–84 months) offer lower monthly payments, they cost significantly more in total interest. For example, a $30,000 loan at 6% costs about $3,500 in interest over 48 months but $5,800 over 72 months. Longer terms also increase the risk of being underwater. Stick to 60 months max for new cars and 36–48 months for used cars if possible.

How does a trade-in reduce my sales tax?

In most US states, sales tax is calculated on the vehicle price minus the trade-in value. For example, if you buy a $40,000 car and trade in a vehicle worth $15,000, you only pay tax on $25,000 — saving $1,050 at a 7% tax rate. However, some states (California, Hawaii, Kentucky, Maryland, Michigan, Montana, Virginia, and Washington D.C.) do not offer this tax reduction.

Is it better to finance through a dealer or my bank?

Getting pre-approved through your bank or credit union before visiting the dealer is almost always recommended. This gives you a baseline rate to compare against the dealer's offer and negotiating leverage. Dealers sometimes mark up the rate by 1–2% for profit. However, manufacturer financing promotions (0%–2.9% APR) through the dealer can beat bank rates — just compare the total cost carefully.

What fees should I expect when buying a car?

Common fees include: title and registration ($50–$500 depending on state), documentation/dealer fees ($100–$500), sales tax (0–10%+ depending on state), and possibly advertising fees or dealer-added accessories. Always ask for an itemized breakdown of all fees before signing. Some fees are negotiable (dealer fees, accessories), while others are fixed (title, registration, tax).

What does it mean to be underwater on a car loan?

Being underwater (or upside-down) means you owe more on the loan than the car is currently worth. This happens when you make a small down payment, choose a long loan term, or the car depreciates faster than you pay down the principal. New cars lose 20–30% of value in the first year. To avoid this, put at least 20% down, choose a shorter term, and avoid rolling negative equity from a previous loan into a new one.

Can I pay off my auto loan early?

Most auto loans allow early payoff without penalties, but check your loan agreement for prepayment clauses. Paying extra toward principal each month — even $50–$100 — can save hundreds or thousands in interest and shorten your loan term significantly. Focus extra payments early in the loan when the interest portion of each payment is highest.