You Have an Extra 500 Dollars a Month and a 6.24 Percent Car Loan. Here Is the Math on Whether to Pay It Off, Refinance, or Invest

TL;DR

• On an $18,000 loan at 6.24% APR with 48 months left, adding $500 per month to your payment pays it off in 21 months and saves $1,359 in interest
• Refinancing at 4.99% (best available for 720+ scores today) saves only $493 over the life of the loan — far less than early payoff
• Investing the $500 monthly at a 10% historical return earns roughly $1,018 in 21 months, but you still pay $2,386 in loan interest — a net loss vs payoff
• Verdict: pay it off early unless you have high-interest debt (above 10%) that should be cleared first

Key Numbers at a Glance

All calculations use standard amortization math on an $18,000 balance at 6.24% APR. Last verified: April 2026.

The Three Options, Honestly

Option 1: Pay It Off Early

At $924.71 per month (your $424.71 minimum plus $500 extra), you pay off the loan in 21 months instead of 48. Total interest paid: $1,027. Total savings vs minimum payments: $1,359.

This is a guaranteed, risk-free return equivalent to 6.24% annualized on every dollar applied to the loan. You cannot get that rate risk-free anywhere else right now.

Bonus: 27 months of freed-up cash flow after payoff. Once the loan is gone, that $924.71 per month can be redirected to investing at a point when markets may be in a better position.

How we calculated this

Standard amortization with extra monthly principal payments. Each month: interest equals balance times monthly rate (6.24% divided by 12 = 0.52%). Payment applied to interest first, remainder to principal. Repeated until balance reaches zero. No prepayment penalties assumed — standard for auto loans in the US.

Option 2: Refinance

Current auto refinance rates for borrowers with 720+ credit scores are running 6.8% to 9% at most lenders in April 2026, per Bankrate's refinance rate survey. At 6.24%, you may already be at or near the best available rate.

If you can get 4.99% (the floor at lenders like Southeast Financial CU or iLending for qualified borrowers), you save $493 over 48 months — about $10 per month. That's meaningful but far smaller than early payoff savings.

Refining makes most sense when:

• Your current rate is above 8% and you've built credit since origination
• You're early in the loan (large remaining balance amplifies savings)
• You can get a rate at least 1.5 to 2 points lower than your current rate

At 6.24% with 48 months remaining, the math only works if you find a rate below 5.5%.

Option 3: Invest the $500/Month

The classic argument: if the market historically returns 10% and your loan costs 6.24%, you come out ahead by investing.

The math in this specific scenario:

• Invest $500/month for 21 months at a 10% annualized return: $12,018 future value, $1,018 in gains
• But you still pay $2,386 in loan interest over 48 months
• Net position: $1,018 gain minus $2,386 interest cost = net loss of $1,368

The investing option only wins if your returns exceed your loan rate by enough to cover the loan interest, and you stay invested long enough for compounding to catch up. At 6.24% APR on a 4-year loan, that break-even takes longer than the loan itself.

The real risk with investing instead: markets don't deliver 10% every year. In 2022, the S&P 500 dropped 18.1%. If you invest instead of paying off the loan and the market drops, you've lost investment value AND still owe the full loan interest. Early payoff is the only guaranteed return in this equation.

When Investing Beats Payoff

The conventional wisdom is right in certain conditions:

1. Your rate is very low (below 3.5%): at sub-inflation rates, the market almost certainly outperforms long-term
2. You have an employer 401(k) match: free money from a match is a 50-100% guaranteed return — always prioritize this first
3. Your time horizon is long: a 20-year investment horizon smooths out volatility; a 4-year loan window doesn't
4. You have an emergency fund: investing makes sense only after you have 3 to 6 months of expenses in cash; a car breakdown or job loss otherwise forces you into high-interest debt

The 5-Step Decision Checklist

1. Check your current rate against today's refi rates (2 minutes): visit Bankrate or NerdWallet. If your rate is already below 6%, refinancing is probably not worth the paperwork. Takes 2 minutes.

2. Check for prepayment penalty (1 minute): call your lender and ask "does my loan have a prepayment penalty?" Almost no US auto loans do, but worth confirming. Script: "I'd like to know if there's any prepayment penalty on my loan account."

3. Calculate your actual savings (5 minutes): use your remaining balance, current APR, and remaining months. Run both scenarios — extra payments and refi — with a loan calculator. Compare the numbers, not just the monthly payment.

4. Check for employer 401(k) match: if you have uncaptured employer match, fund that first before extra loan payments. It's the only truly guaranteed double-digit return available.

5. Build or verify emergency fund: 3 to 6 months of expenses in a HYSA. If you don't have this, a sudden repair or job loss puts you back in debt immediately — negating any payoff benefit.

FAQ

Is 6.24% a good auto loan rate in 2026? Yes, for most borrowers. The average new car loan rate is around 7.1% and used car loans average higher. A 6.24% rate suggests a solid credit score (700+). Refinancing to a meaningfully lower rate is difficult at this starting point.

What if I can get a 4% refi rate? Then refinancing becomes more competitive. At 4% APR on the same $18,000 balance: total interest drops to $1,499, saving $887 vs the current loan. Still less than the $1,359 from early payoff, but you keep the $500/month liquid.

Should I pay off the car or build an emergency fund first? Emergency fund first if you have less than 3 months of expenses saved. The car payoff math breaks down the moment a surprise expense forces you to take on a personal loan at 15% or carry a credit card balance at 24%.

Does paying off early hurt my credit score? Temporarily, yes. Closing an installment loan typically drops your score by 5 to 15 points for a few months. Long-term, it has no negative effect and frees up your debt-to-income ratio.

What if I have $10,000 lump sum instead of $500/month? Apply it directly to principal immediately. On this loan, a $10,000 lump sum today reduces total interest from $2,386 to approximately $441 — saving $1,945. Lump sum paydowns are more powerful early in the remaining term.

The Bottom Line

At 6.24% APR in April 2026, the math is clear: paying off early saves more than refinancing and beats investing on a risk-adjusted basis for this specific loan size and term.

The one exception worth checking first: your 401(k) match. If your employer will match your contributions up to a certain percentage and you're leaving that match uncaptured, fund that before the extra car payment. It's the only guaranteed return that beats 6.24% without taking market risk.

Everything else: pay the car off.

Sources

• Bankrate, auto refinance rate survey, April 2026
• Bankrate, auto loan calculator
• NerdWallet, auto loan calculator
• Dollar Times, loan amortization reference