Automakers are reporting the best two-month stretch of U.S. sales in 15 years, another sign that the nation's economy is improving.

General Motors Co. and Fiat Chrysler Automobiles NV were among manufacturers posting October results that topped analysts' estimates after a robust September, with the continued popularity of expensive trucks and luxury sport utility vehicles showing that buyers are willing to spend. Ford Motor Co. and Honda Motor Co. fell short of predictions.

The burgeoning demand for autos is adding to evidence the U.S. economy is strengthening as the Federal Reserve prepares to raise interest rates as soon as next month. Sales are surging as job growth, available credit and affordable fuel encourage shoppers to replace aging models, especially with sport utility vehicles.