Zero-percent financing and cash-back rebate offers are as much a part of auto sales as gleaming showrooms and that new-car smell. The options also pose a puzzle for shoppers: Which one is better for the pocketbooks?

While the words "zero-percent financing" can have a powerful tug when it comes buying a new car, analysts say it is not always the better choice. A buyer may be better off choosing the cash-back rebate in cases where the loan has to be repaid in 24 to 36 months. But zero-percent financing that lasts five years or longer can be very attractive.

"It offers consumers interest-free financing, which is a lot of incentive. If they finance, it is better for them to take advantage of (zero percent financing over five or more years). They can save money. Normally the rebate is $1,000, $1,500 or $2,000, but the finance interest incentive averages $3,500 to $5,000," said Obaid Nabizada, a finance manager at Hayward (Calif.) Nissan.

Of course, when it comes to buyers who pay upfront with cash or a personal check, then a cash-back rebate is the only option, he said.

Unlike regular car loans, in which consumers have the option of going to a bank or credit union, zero-percent financing requires manufacturer-backed financing offered through car dealerships. In addition, a good credit score - generally 700 or above - is needed, which means most buyers who seek zero-percent financing do not get it, said Liz Opsitnik, editor of

Zero-percent interest loans typically are offered in the range of 24 to 36 months.

However, a 60-month or longer term has recently become more available, and it was offered on 13 of the 20 featured vehicles on a list of manufacturer-backed promotions running during June.