0% Financing Beats $3,000 Cash Back Unless Your Rate Is Under 3.7%

Manufacturers subsidise sales two ways: a promotional finance rate, or a cash rebate off the price. They rarely allow both, and the choice is presented as a matter of preference. It is not. One of them is arithmetically better for you, and which one depends on a single number.

The comparison

A $34,000 vehicle over 60 months. Option A is 0% financing at full price. Option B is a $3,000 rebate, financing $31,000 at a market rate of 7.4%.

The 0% offer wins by $3,182.26, and it also has the lower monthly payment despite financing $3,000 more. Both facts follow from the same cause: at 7.4% over five years, the interest on $31,000 exceeds the $3,000 you were given to accept it.

The break-even rate

Solve for the interest rate at which the rebate option exactly matches 0% financing. On these figures it is 3.70%.

The break-even moves with the size of the rebate, the price, and the term. A larger rebate or a shorter term pushes it upward, sometimes far enough to reverse the answer. A $5,000 rebate on the same car over 36 months has a break-even in double digits, and the rebate wins comfortably.

When the rebate wins

• You are paying cash. The 0% financing is worth nothing to a buyer who is not borrowing, so the rebate is a straight $3,000 discount. Never mention that you intend to pay cash until the price and any rebate are agreed.
• You will repay quickly. Financing $31,000 for twelve months at 7.4% costs far less than $3,000, so the rebate wins for a buyer clearing the loan early.
• You have access to a genuinely low rate, such as a promotional credit union offer or a secured line below the break-even.
• You have a large down payment. The smaller the amount financed, the less the interest matters and the more the fixed rebate is worth.

The complications dealers rely on

1. The 0% rate is usually restricted to the strongest credit tiers and to specific models, trims, and terms. An advertised 0% for 60 months frequently becomes 1.9% for 48 months once your application is assessed, which changes the comparison entirely.
2. Promotional rates often require shorter terms. A 0% offer over 36 months carries a much higher payment than a 72-month market-rate loan, and a buyer who cannot afford it is steered to the rebate by default rather than by choice.
3. The negotiated price may differ between the two paths. Some dealers are less flexible on price when you take subsidised financing, which quietly erodes the advantage. Agree the out-the-door price before discussing how you will pay.
4. Rebates come in stackable categories, including loyalty, military, and recent-graduate incentives. These sometimes combine with promotional financing even when the headline cash rebate does not.

Doing it yourself

Take the price, the rebate on offer, the term, and the best rate you can independently obtain. Compute the payment on the rebate route, multiply by the term, and compare that total to the full price. If the total exceeds the price, the 0% offer is cheaper. That is the whole calculation, and it takes less time than the test drive.