Should You Use a 401(k) Loan to Buy a Car?

By John Brandenburg. Last updated June 26, 2026.

A 401(k) loan can look attractive when auto loan rates are high. You borrow from your own retirement account, usually without a traditional credit application, and the interest you pay generally goes back into your account rather than to a bank. On paper, that can make the loan look cheaper than dealer or bank financing.

The tradeoff is that borrowed money is no longer invested while it is out of the plan. The real cost is not just the stated 401(k) loan rate. It is the difference between what the borrowed balance earns through repayments and what it might have earned if it had stayed invested.

Why the interest rate can mislead you

Imagine a $35,000 401(k) loan at 5.5% over five years. The interest goes back to your account, which sounds like paying yourself. But if the market earns 8% during that period, the account may still end up behind because a large balance missed part of that compounding window.

If the market performs poorly, the 401(k) loan may look better in hindsight. That uncertainty is why the calculator uses a market-return assumption and sensitivity analysis. A strategy that wins at a 4% expected return can lose at an 8% expected return.

The employment risk

The biggest non-math risk is job change. Many plans require faster repayment after employment ends. If the outstanding balance is not repaid on the plan's schedule, it may be treated as a taxable distribution. For younger workers, that can also create an early-distribution penalty.

That risk is easy to underweight because it is not part of the monthly payment. If your job situation is uncertain, a 401(k) loan is riskier than it looks in a simple rate comparison.

When it may make sense

• Your plan allows loans with reasonable fees and repayment terms.
• Your employment is stable enough that acceleration risk is low.
• Available auto loan rates are materially higher than the 401(k) loan rate.
• The loan would not drain your retirement account or replace an emergency fund.
• You have modeled the opportunity cost instead of only comparing rates.

When to be cautious

Be cautious if the loan would represent a large share of your retirement balance, if your employment could change, or if you are using the 401(k) loan to buy more vehicle than you would otherwise buy. The fact that the payment is available does not make the purchase cheap.

Use the calculator to compare a 401(k) loan with dealer financing and taxable investment liquidation. Before acting, verify your own plan's rules. The IRS publishes a general overview of retirement plan loan rules, but employer plans can be more restrictive than the general limits.

This article is educational only and is not financial, tax, legal, lending, or investment advice.