What is Car Loan?
An auto loan finances the purchase of a vehicle by spreading the cost over monthly payments plus interest. Understanding the total cost of borrowing, not just the monthly payment, is essential for making a financially sound vehicle purchase. Compare with total ownership costs using the Vehicle Cost Calculator.
The Formula
Monthly Payment = [Loan Amount × Monthly Rate × (1 + Monthly Rate)^Months] ÷ [(1 + Monthly Rate)^Months − 1]
Monthly Rate = Annual Rate ÷ 12. Total Interest = (Monthly Payment × Number of Months) − Loan Amount.
Worked Example
A $30,000 car with a $5,000 down payment, leaving a $25,000 loan at 6.5% APR over 5 years (60 months).
- Loan amount = $30,000 − $5,000 = $25,000
- Monthly rate = 6.5% ÷ 12 = 0.542%
- Monthly payment = $489
- Total repaid = $489 × 60 = $29,340
- Total interest = $29,340 − $25,000 = $4,340
📌 Monthly payments of $489 over 5 years, with $4,340 in total interest, 17.4% of the loan amount. The car actually costs $34,340 including interest and down payment.
Why This Matters
Total cost awareness
Dealers emphasize monthly payments ("only $399/month!") to distract from the total cost. A lower monthly payment over a longer term means more interest. Always calculate the total amount repaid before committing. CFPB auto loan research shows that the average 72-month new car loan at 7% APR generates $7,800 in total interest on a $30,000 vehicle, compared to $4,200 on a 48-month loan at the same rate, a $3,600 difference that is invisible when only monthly payments are compared.
Depreciation overlap
Cars depreciate 15-30% in year one and 45-55% over 3 years. If your loan term exceeds the car's depreciation curve, you may owe more than the car is worth (negative equity). This creates problems if you need to sell or trade in early. Edmunds depreciation data shows that 44% of trade-ins carry negative equity averaging $5,400, meaning these buyers are rolling prior debt into a new loan and paying interest on the old car while financing the new one.
Credit score impact
Auto loans affect your credit profile in two ways. The initial hard inquiry and new account lower your score by 5-15 points short term. But consistent on-time payments over 12-24 months build credit history and improve your score. Experian data shows borrowers with auto loans in good standing average 20-40 points higher than those without installment loan history, and that borrowers who shop multiple lenders within a 14-day rate-shopping window incur only one hard inquiry regardless of how many lenders pull their credit.
Common Mistakes
❌ Extending the term to reduce payments
A 7-year loan reduces monthly payments but you pay interest for 2 extra years. On a $25,000 loan at 6.5%, extending from 5 to 7 years saves $90/month but adds $2,200 in total interest.
❌ Not comparing finance types
Dealer financing, bank loans, and credit union loans have different rates and total costs. Credit unions often offer rates 1-2% lower than dealers, and getting pre-approved strengthens your negotiating position.
❌ Skipping the down payment
Zero-down loans put you underwater on day one because the car depreciates the moment you drive off the lot. A 20% down payment reduces the loan principal, lowers monthly payments, and provides an equity cushion. On a $30,000 car, 20% down ($6,000) saves roughly $1,200 in interest over a 5-year loan at 6.5% APR.
Industry Benchmarks
| Category | Good | Average | Poor |
|---|---|---|---|
| APR | Below 5% | 5-8% | Above 10% |
| Total interest as % of loan | Below 15% | 15-25% | Above 30% |
| Loan-to-value ratio | Below 80% | 80-100% | Above 100% (underwater) |
Source: Experian State of the Auto Finance Market & AAA Your Driving Costs Report
Benchmark data sourced from Experian State of the Auto Finance Market & AAA Your Driving Costs Report.