The cost of living in the U.S. was unchanged in September, restrained by declines in fuel costs, automobile prices and airline fares that show the slowing economy is starting to cool inflation.

The Labor Department’s consumer price index was unchanged after a 0.1 percent drop in August; economists had forecast an increase for last month. So-called core prices, which exclude food and energy, rose 0.1 percent, also less than forecast.

Today’s figures show that for the first time in two years, prices didn’t increase for two straight months. Waning inflation gives Federal Reserve Chairman Ben S. Bernanke scope to lower interest rates further as policy makers attempt to unfreeze credit markets.