Monthly certified pre-owned sales fell on a year-over-year basis for the first time since June 2014, but year-to-date sales are still more than 10 percent ahead and four brands posted best-ever sales results.

There were 220,416 certified sales in August, which was off 1.1 percent from August 2014, according to a roundup of CPO sales from Autodata Corp.

Granted, there was one less selling day in August of this year. The daily selling rate for this most recent month (8,478) beat the year-ago figure by 2.7 percent.

And through eight months, CPO sales have reached 1.72 million units, which is a 10.4-percent improvement over the year-ago time frame.

Posting all-time highs in August were Nissan, Infiniti, Mini and Porsche, Autodata pointed out.

So, much like the last time CPO sales fell, take this drop with a grain of salt.