Certified pre-owned vehicles made up more than a fifth of franchised dealers’ used-car sales in the second quarter — and CPO may not have even yet reached its full potential.

Edmunds.com said in its Q2 Used Vehicle Market Report that 20.4 percent of used sales at franchised dealerships last quarter were certified units. The share of used site traffic commanded by CPO dipped for the second straight quarter, however, coming in at 4.9 percent.

“While CPO has seen a slight bump in share, there still is plenty of room for growth,” the company’s analysis noted. “This market helps bridge the gap for car shoppers buying used but still receiving some of the new-vehicle peace of mind.”

Part of certified pre-owned’s growth can likely be attributed to stronger lease returns.

For instance,  Ford Credit’s lease return volume already eclipsed the 100,000-unit mark in just two quarters of 2014, according to data from Ford Motor Co.’s Q2 fixed income conference call that Manheim chief economist Tom Webb posted to his blog in July.

More specifically, off-lease volume for Ford Credit through six months of 2014 was in the neighborhood of 110,000 units — again, just through six months. For full-year 2013, it was around 114,000.

“Big increases in lease returns typically apply downward pressure on prices but create  opportunities to certify and sell more CPO vehicles. Lease returns generally meet manufacturer's eligibility requirements for certification because of low mileage, condition and age,” the Edmunds report noted. “CPO sales command higher prices and minimize impacts to transaction prices.”

Case in point: franchised dealers had average used-car transaction prices of $16,781 during the second quarter, which is the highest amount Edmunds said it has ever recorded.