LAWRENCEVILLE, Ga. — Black Book (a div. of Hearst Business Media)’s Used Vehicle Retention Index rose modestly in June, increasing from 112.3 in May to 113.0. On a 12-month basis, the index has dropped 4.5% from last June.

It was the second time in the past three months the index registered an increase — April’s reading showed a slight increase due to a stronger-than-expected spring selling season for used vehicles. The index’s rise in June was due in large part to falling gas prices, which helped drive the sale of used trucks, crossovers and SUVs. The downside of falling gas prices was the continued acceleration in depreciation for subcompact and compact cars, the firm noted.

“In addition to falling gas prices, which are playing a role in driving a little more interest for certain trucks today, there are generally some very good deals out there for used vehicles currently,” said Anil Goyal, senior vice president of automotive valuation and analytics for Black Book. “These are the primary reasons why we are seeing some bounce off the lows in used car retention trends.”

The Index dates back to January 2005, when Black Book published a benchmark index value of 100.0 for the market. During 2008, the index dropped 14.1%. During 2011, the index rose strongly from 113.3 to 123.0 by the end of the year, as the economy picked up steam and used-vehicle values rose higher. It continued to remain relatively stable, rising slightly until May of 2014. That’s when the index peaked 128.1.

Last year, the index fell by just 6.4%.