(MONEY Magazine) – I bonds are now paying their biggest premium over inflation in three years: a fixed rate of 1.4%, up from 1%, and good for up to 30 years. But you may only get this deal if you buy before rates reset in the fall. That's because the payout on these savings bonds is made up of two parts: the fixed rate, which represents a margin over inflation, and a variable portion (now 1%) tied to the consumer price index and adjusted twice a year. Savings bond expert Daniel Pederson expects that when new rates hit on Nov. 1, if inflation stays at its recent pace, the fixed rate will drop to 1%, but the variable part will jump as high as 5.5%. Invest before then and your total payout would be almost 7% for the following six months.

• WARNING You can't redeem I bonds for one year. Can't wait? Stick with a money market or CDs.

SAVINGS

CREDIT

SAVINGS NOTES AND SOURCES: CD and money-market account data as of May 23 from 100 Highest Yields ($124 for 52 issues; 800-327-7717); all have a minimum investment of $10,000 or less. Average tax-exempt and taxable money-market fund yields for the week ending May 23 from Money Fund Report (imoneynet.com); all have a minimum investment of $10,000 or less and assets of $25 million or more. Average bond fund yields are for the month ending April 30 from Lipper; all are medium- and high-quality funds without sales loads and with average maturities of three years or less. [1] Manager absorbed all or some operating expenses. [2] Closed to new investors, except Bank of America customers. CREDIT NOTES AND SOURCES: All rates subject to change. Credit-card rates are for standard cards as of May 23 from Bankrate.com and are variable unless otherwise indicated. Survey does not include Internet-only cards or AmEx Blue. [1] Visa only. [2] Fixed rate. [3] Platinum and gold cards.