(MONEY Magazine) – Mortgages aren't the only loans you can refinance. In today's falling-rate environment, car and student loans have become candidates as well--but only for certain borrowers. Here's what you need to know about cutting your rate.

Car loans. It's often not worth refinancing a car loan, since used-car loans carry higher rates and car-loan terms are short--four or five years--leaving you little time to recoup any fees. But nowadays, some banks and credit unions are offering such low rates that it's worth a look. PeopleFirst.com, for example, was recently offering refinancing loans as low as 6.75%. You can search for rates in your area at www.bankrate.com. Consider refinancing only if you borrowed in the past two years, and match the loan to your remaining term so that you don't pay more in total interest.

Student loans. If you consolidate your federal loans with a lender like Sallie Mae (800-448-3533; www.salliemae.com), you can lock in today's interest rate. But the only borrowers who should consider this are recent graduates who have not yet started repaying their loans and can lock in a 5.5% rate now. Everyone else should wait until the spring, says Kalman Chany, author of Paying for College. Rates on federal loans are adjusted annually on July 1, based on the 91-day Treasury bill, so anyone repaying a Stafford Loan is now paying just 5.99%. The new rate will be announced in May. If next year's rate is lower than 6%, consolidate after July 1; if it's higher, you can still lock in 6% in June. Keep in mind, though, that if you stretch out the term of your loan with a consolidation, you could end up paying more in interest. So take as short a term as you can manage

--LAURA PERRY