Enter the vehicle price, your deposit or trade-in, the rate and the term. You get the monthly payment, the total interest over the life of the loan, and the share of the price you are actually financing - the number that tends to surprise people once a long term is involved.
Cars depreciate faster than a long loan amortises, so for years you owe more than the car is worth. If it is written off or you need to sell, the shortfall is yours. Longer terms also multiply the total interest even at the same rate.
Work out both. A rebate reduces the amount financed immediately; subsidised finance reduces the interest on a larger balance. On shorter terms the rebate usually wins, on longer ones the low rate. Run the numbers twice rather than assuming.