A friend bought a car at 18% for 72 months.
They are proud of the payment. They have not done the multiplication. You want to say something — without sounding superior, without rupturing the friendship, and without pretending the past can be undone.
$525 a month sounds fine. Multiply it.
Almost every car-loan conversation gets stuck on the monthly payment. The salesperson talks in months. The buyer thinks in months. The number that matters — the total over the life of the loan — never gets said out loud.
Principal, interest, total.
The salesperson talks in months. The buyer thinks in months. The number that actually matters — the total over the life of the loan — never gets said out loud.
That second bar is the cost of borrowing. It buys nothing. It does not sit in the driveway. It is the price of spreading the payment out long enough to make it feel small.
And the car is not waiting for them to finish paying.
Cars lose value on a schedule that does not care about the loan schedule. A new car typically loses about 20% in year one and around 60% by year five. While the friend pays $525 every month, the car keeps shedding worth in the other direction.
Paid climbs. Resale falls.
Cars lose value on a schedule that doesn't care about the loan schedule. The two lines cross around month 29 — and after that, more goes out than the car is worth.
By month 72 they have paid $37,770 for an $8,000 car. The other $29,770 is gone.
Run the 20/3/8 rule. Every check fails.
The Money Guy Show’s 20/3/8 rule is the cleanest pre-buy check anyone has put on the table for car purchases. Three numbers, one car. When all three pass, the math stays out of the way of the rest of the financial plan.
20/3/8, applied.
Brian Preston's 20/3/8 rule from the Money Guy Show: 20% down · 3-year loan · payment ≤ 8% of gross monthly income. Three numbers, one car.
The rule is not a moral judgment — it is the test that, when passed, keeps a car from quietly eating a decade of someone’s wealth-building. When all three fail, that is exactly what is happening.
What that interest was also doing.
Money sent to a lender as interest cannot be invested. That opportunity cost compounds. If your friend is 25 and the interest portion alone had instead landed in a Roth IRA earning the long-run market average, here is what it would have grown into by age 55:
This is the math that almost never makes it into a car conversation. Not because it is hidden — because nobody runs it.
Three doors still open.
Your friend already signed. The past is sunk. But three real moves change the trajectory of this loan — and at least one of them is almost always worth doing.
Three moves, priced.
The past is sunk. But three real moves change the trajectory of this loan — at least one is almost always worth doing.
Refinance to a credit union.
Credit unions routinely write used-car loans at 5–8% for borrowers with reasonable credit. Even a drop from 18% to 8% on the remaining balance saves thousands and shrinks the cliff (panel 6) at the same time.
Aggressive payoff.
Every extra dollar against principal at 18% earns a guaranteed 18% — better than almost any investment. $100/mo extra cuts months off the loan and kills interest.
Sell now, buy a used car cash.
Market value at month 12 is $19,288; loan payoff is $20,658 — friend writes a $1,370 check to settle the gap and buys a $7,000 used car cash. Hardest emotionally; biggest impact.
Door 1 is the lowest-friction move and is almost always available. It is also the easiest to suggest in conversation — you are not telling them they bought the wrong car, just that they bought it at the wrong rate.
The cliff if they cannot pay.
Most borrowers do make their payments. But if something cracks — job loss, medical, divorce — the cliff is steeper than most realize. Your friend should know what is on the other side before they have to find out.
- 30–60 days late. Most lenders can repossess after roughly two missed payments. In most US states the lender can hire a tow without a court order (UCC § 9-609), as long as they avoid breaching the peace.
- The auction shortfall. Repossessed cars typically sell at auction for 30–50% below market. The borrower still owes the deficiency balance — the difference between the auction proceeds and the loan payoff.
- The credit damage. A repo drops the credit score by 100+ points and stays on the report for seven years. The next auto loan, if approved at all, is at 25%+ or sub-prime terms.
If the payments are already stretching, the right move is to act before the cliff lands. Two options exist before voluntary surrender becomes the last reasonable step:
- Sell while you can. Same as Door 3 above, but the rule shifts — if the car is underwater, write a check for the gap rather than letting the auction take it. The deficiency lands either way; a private sale at full market beats an auction by thousands.
- Voluntary surrender. Slightly less brutal on credit than involuntary repo, but it still shows as a repo on the report. Use it only when sell-private is not viable and missed payments are otherwise about to stack.
- Non-profit credit counseling. If the car is part of a larger debt picture, NFCC-accredited counselors negotiate with lenders before things crack. Bankruptcy is the last resort and outside this lesson’s scope.
Door 1 (refi) and Door 2 (extra principal) both shrink this cliff. Door 3 jumps over it. Doing nothing walks toward it.
How to have the conversation.
Math does not change minds — relationships do. Lead with the relationship; offer the math only if they ask for it.
- Lecture, calculate at them, or send them a spreadsheet.
- Use the words “you should have” — they signed; that ship sailed.
- Bring it up the first time you see the car.
- Compare it unfavorably to your own car.
When the right moment comes — they are complaining about the payment, or asking what you would do — these three sentences open the door without knocking it down:
How are you feeling about that monthly? I have heard some people refinance through a credit union after a few months — sometimes the rate drops a lot.
If you ever want a hand running the numbers — what the loan actually costs at 18% versus 8% — I am happy to. No pressure.
Whatever you decide, I am in your corner.
If they say yes, walk them to Door 1. If they do not, drop it. The friendship lasted before this car and will last after it.
The lesson is not about cars. It is about monthly payments.
Anything sold in months — cars, furniture, electronics, “buy now, pay later” — uses the same trick: a number that sounds fine multiplied by a horizon long enough to make it survivable. Once you can run the multiplication, the pitch loses its grip.
- $525 a month for 72 months is $37,770. Always multiply.
- Cars depreciate on a schedule that ignores the loan schedule.
- The 20/3/8 rule is the cleanest pre-buy check — three numbers, one car.
- A friend who already signed is not out of moves. Door 1 alone saves thousands.
- If payments are stretching, sell-private beats waiting for the auction.
- Lead with the relationship; offer the math only when they want it.