U.S. auto sales volume is expected to keep rolling along in August, with two independent forecasters predicting a sixth straight month of 16 million-plus selling rates.

TrueCar.com predicts a seasonally adjusted annual selling rate of 16.6 million for August, and LMC Automotive/J.D. Power is just behind at 16.5 million. Both expect 1.5 million light vehicles to be sold, equaling a strong August a year ago despite one fewer selling day this year. The August 2013 SAAR was 15.9 million.

"We remain upbeat about auto industry sales, segment mix and profitability," said TrueCar President John Krafcik, noting August incentives climbed an estimated 9.3 percent.

"Incentive spending changes reflect consumer demand shifting to higher-MSRP, higher-profit vehicle segments, which is a net positive for most full-line auto makers," he said.

John Humphrey, head of the global auto practice at Power, expects August spending on new vehicles to reach almost $39 billion. That would be the second-highest revenue for any month on record, trailing only $39.7 billion spent in July 2005.

"The record consumer spending is fueled by both high sales volumes and high transaction price."he said.