Can AI compare car loan offers?
Yes. Give it each offer's rate, term and fees and it shows the monthly payment and total interest side by side, so a lower payment doesn't hide a more expensive loan.
01Why bot
- Loan math is exact and AI shows its work.
- Longer terms often lower the payment but raise the total cost; it makes that visible.
- Always double-check the math with a loan calculator.
Sponsor slot · openFeatured tool for this task. A labeled card for one relevant tool.
Book this spot →02The prompt
Replace everything in [BRACKETS] with your own details, then paste it into your AI app.
You are a consumer lending advisor. This is not financial advice. Amount to borrow: [AMOUNT] Offers: [LENDER: RATE (APR), TERM IN MONTHS, FEES] Your task: compare the loans. Rules: - MUST show the monthly payment and total interest for each, with the formula inputs. - MUST point out the cheapest total cost, not just the lowest payment. - NEVER assume fees I didn't list. Give me: a comparison table and a one-line recommendation.
03Steps
- Get loan offers from your bank or credit union, not just the dealer.
- Run the prompt.
- Confirm payments with an online loan calculator.
04What can go wrong
- AI math can slip; verify.
- Your final rate depends on your credit approval.
05What to use
Any major AI chat app.
06Our test runs
2 runs, each with a different made-up sample. 2 of 2 passed every check.
Run 1 · Llama 3.3 70B · graded by GPT-OSS 120BOct 4, 2026Passed
The made-up sample:
[AMOUNT]$25,000[LENDER: RATE (APR), TERM IN MONTHS, FEES]Bank A: 4.9% APR, 60 months, $300 fee; Credit Union B: 4.5% APR, 72 months, $150 fee; Online Lender C: 5.2% APR, 48 months, $0 fee
- Show monthly payment and total interest with formula inputs
- Point out cheapest total cost, not just lowest payment
- Never assume fees not listed
- Provide comparison table and one-line recommendation
- Didn't make up details we never gave it
What came back (excerpt):
To compare the loans, we'll calculate the monthly payment and total interest for each option.
Read the full answer
To compare the loans, we'll calculate the monthly payment and total interest for each option. 1. Bank A: - Monthly payment: $479.46 = $25,000 * (4.9%/12) / (1 - (1 + 4.9%/12)^(-60)) - Total interest: $6,366.91 = $479.46 * 60 - $25,000 - Total cost: $6,366.91 (interest) + $300 (fee) = $6,666.91 2. Credit Union B: - Monthly payment: $393.95 = $25,000 * (4.5%/12) / (1 - (1 + 4.5%/12)^(-72)) - Total interest: $6,287.41 = $393.95 * 72 - $25,000 - Total cost: $6,287.41 (interest) + $150 (fee) = $6,437.41 3. Online Lender C: - Monthly payment: $566.14 = $25,000 * (5.2%/12) / (1 - (1 + 5.2%/12)^(-48)) - Total interest: $4,917.12 = $566.14 * 48 - $25,000 - Total cost: $4,917.12 (interest) + $0 (fee) = $4,917.12 Comparison table: | Lender | Monthly Payment | Total Interest | Total Cost | | --- | --- | --- | --- | | Bank A | $479.46 | $6,366.91 | $6,666.91 | | Credit Union B | $393.95 | $6,287.41 | $6,437.41 | | Online Lender C | $566.14 | $4,917.12 | $4,917.12 | Recommendation: Based on the total cost, Online Lender C is the cheapest option, with a total cost of $4,917.12.
Watch that fees are only those listed.
Run 2 · Llama 3.3 70B · graded by GPT-OSS 120BOct 26, 2026Passed
The made-up sample (a messier one):
[AMOUNT]15,300[LENDER: RATE (APR), TERM IN MONTHS, FEES]BankA: 4.9% (APR), 60, $299 origination fee; CreditUnionB: 5.2% (APR), 72 months, $0; AutoFinC: 4.7% (APR), 48, $450 processing fee; LenderD: 5.0% (APR), 60 months, $199; LenderE: 5.1% (APR), term 60 months, fee TBD
- Show monthly payment and total interest for each
- Include formula inputs
- Point out cheapest total cost
- Never assume fees not listed
- Didn't make up details we never gave it
What came back (excerpt):
lculate the monthly payment and total interest for each option using the formula for monthly payment: M = P[r(1+r)^n]/[(1+r)^n – 1], where M = monthly payment, P = principal loan amount, r = monthly interest rate, and n = number of payments.
Read the full answer
To compare the loans, we'll calculate the monthly payment and total interest for each option using the formula for monthly payment: M = P[r(1+r)^n]/[(1+r)^n – 1], where M = monthly payment, P = principal loan amount, r = monthly interest rate, and n = number of payments. Here are the calculations: 1. **BankA**: P = $15,300, r = 4.9%/12 = 0.004083, n = 60. M = $15,300[0.004083(1+0.004083)^60]/[(1+0.004083)^60 – 1] = $293.41. Total interest = $15,300 * 0.004083 * 60 - $293.41 * 60 + $299 = $4,051.19 + $299 = $4,350.19. 2. **CreditUnionB**: P = $15,300, r = 5.2%/12 = 0.004333, n = 72. M = $15,300[0.004333(1+0.004333)^72]/[(1+0.004333)^72 – 1] = $251.45. Total interest = $15,300 * 0.004333 * 72 - $251.45 * 72 = $3,513.36. 3. **AutoFinC**: P = $15,300, r = 4.7%/12 = 0.003917, n = 48. M = $15,300[0.003917(1+0.003917)^48]/[(1+0.003917)^48 – 1] = $348.17. Total interest = $15,300 * 0.003917 * 48 - $348.17 * 48 + $450 = $1,883.89 + $450 = $2,333.89. 4. **LenderD**: P = $15,300, r = 5.0%/12 = 0.004167, n = 60. M = $15,300[0.004167(1+0.004167)^60]/[(1+0.004167)^60 – 1] = $286.51. Total interest = $15,300 * 0.004167 * 60 - $286.51 * 60 + $199 = $3,000.03 + $199 = $3,199.03. 5. **LenderE**: Since the fee is TBD, we cannot accurately calculate the total cost. Thus, we'll only calculate the monthly payment and interest without the fee: P = $15,300, r = 5.1%/12 = 0.00425, n = 60. M = $15,300[0.00425(1+0.00425)^60]/[(1+0.00425)^60 – 1] = $289.15. Total interest without fee = $15,300 * 0.00425 * 60 - $289.15 * 60 = $3,067.50. Comparison table: | Lender | Monthly Payment | Total Interest | | --- | --- | --- | | BankA | $293.41 | $4,350.19 | | CreditUnionB | $251.45 | $3,513.36 | | AutoFinC | $348.17 | $2,333.89 | | LenderD | $286.51 | $3,199.03 | | LenderE | $289.15 | TBD (fee unknown) | Recommendation: Based on the lowest total cost, **AutoFinC** offers the cheapest option, despite having a higher monthly payment, with a total interest of $2,333.89.
Check the total interest calculations for accuracy.
How each run works: we fill the prompt with a made-up sample, run it once in Llama 3.3 70B, and GPT-OSS 120B grades the answer against the prompt's own rules. Word limits are counted by code, and every quote flagged as made up is checked against the full answer. Your results can differ. How we test.
Prompt packCars: Buying, Repairs & Costs 10 step-by-step prompts that go further than this one, $12.
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