Manufacturer offers usually force a choice: take 0% APR financing OR a cash rebate. Run both numbers and pick the cheaper one.
"0%" sounds like free money. Sometimes it is. Sometimes the cash rebate plus a normal-APR loan saves you more in absolute dollars over the same period. The math depends on the rebate size, the standard APR, the loan term, and how much you finance.
Rule of thumb: the larger the rebate (relative to the loan amount), the more often the rebate-plus-financing path wins. The shorter the term, the more often 0% wins (less interest accrues either way).
Total cost is the number that matters. Whichever option's total cost is lower is the better deal in absolute dollars. The monthly payment numbers help you understand cash-flow impact, but don't override total cost.
Real example: $35,000 vehicle, $3,000 down, 60 months. 0% APR financing pays $32,000 total. $4,000 rebate plus 6.5% APR financing pays $33,790 total. 0% wins by $1,790 in this case.
But if the rebate were $6,000 instead of $4,000, the rebate path wins by $400 — even at the same standard APR. Always run your specific numbers.
Almost never. Manufacturer subvented financing programs require choosing between them. The dealer can't combine them either.
Take the rebate, then either accept the dealer's standard-APR financing (with the rebate offsetting some of the cost) or use a competing pre-approval from a credit union or bank.
The rate quoted by the dealer's finance manager often is — they have markup room above the bank's buy rate. Bring a competing pre-approval to compress that markup.