As the summer season continues, one trend is emerging for medium-duty trucks — declining auction prices, according to Black Book’s August Specialty Markets report.

In June, wholesale prices for model year 2015-2016 medium-duty trucks declined by 0.2%. The next month prices for those same units dropped by an average of 0.4%. The same trend emerged for older units. Trucks from the 2007 to 2014 model years saw prices drop by 0.5% in June, and then 0.7% in July.

The factor that most contributed to this decline was the poor condition of most units arriving at auction.

"The overall condition of the units hitting the auction lanes is showing up in worse and worse condition," according to the report. "We understand this and take this into consideration when evaluating units and adjusting our prices."

On a more positive note, fuel prices are seeing little change on a week-to-week basis, with no significant change expected in the near future, Black Book stated. The current national average for a gallon of diesel is $2.49, roughly 5 cents less than the previous month.