To paraphrase the classic villain line from the old Scooby Doo episodes, it would've been a good June if it wasn't for those meddling Volkswagen diesel and Chevy Malibu sales. Advanced-powertrain vehicle sales in the US halted their upward trajectory last month, and year-over-year demand fell for the first time since February. Americans bought 53,945 hybrids, plug-ins and diesels in June, which marked a 7.6 percent decline from a year earlier. Even factoring the likely uptick in Tesla Model S electric vehicle sales (the company doesn't break out monthly sales numbers, nor does it disclose how many vehicles it sells overseas, hence its exclusion from the totals), green car sales would've still been down. And that's despite the fact that plug-in vehicle sales jumped 42 percent from a year earlier and approached the 10,000-unit mark, even without Tesla.

We have to blame the VW oil burners and Malibu mild-hybrids.

And, of all things, we have to blame the VW oil burners and Malibu mild-hybrids. VW accounted for more than half the US shortfall, as the German automaker's diesel sales plunged 28 percent from a year earlier to 6,456 units, while Jetta Hybrid sales were down 53 percent to just 206 units.

Meanwhile, General Motors also had a real tough month, and it wasn't just because Chevrolet Volt extended-range plug-in sales fell 34 percent to 1,777 units. No, the real culprit was the Chevrolet Malibu Eco, whose June sales virtually disappeared (just 62 units sold) compared to the June 2013 total of 1,651 units. Overall, GM's green-car sales fell 42 percent from a year earlier to 3,204 units.

Prius Plug-in Hybrid sales almost tripled.

Toyota turned in what's looking like a typical month in 2014, with advanced-powertrain sales falling 9.2 percent from June 2013 to 27,846 units. While Prius Plug-in Hybrid sales almost tripled, total sales among the four Prius variants were down 12 percent to 18,649 vehicles, while Camry and Avalon Hybrid sales were both about even with year-earlier totals. Lexus hybrid sales fell 5.5 percent to 3,515 units.

All of that wiped out the effects of yet another positive month for Nissan and strong June demand for both Honda and Ford vehicles. The Nissan Leaf battery-electric boosted sales by 5.5 percent from what was a strong June 2013 to 2,347 units. Honda was buoyed by moving 1,135 units of its newer Accord Hybrid. So while sales of all of its other hybrids were down, Honda boosted its overall green-car sales by 30 percent from a year earlier to 2,290 units.

The Ford Fusion Energi was, for the first time, the best-selling American plug-in on record.

And, in an odd twist, the Ford Fusion Energi Plug-in Hybrid was, for the first time ever, the best-selling American-made plug-in last month (remember, we're not counting Tesla and we'll set aside the fact that the Leaf is assembled in Tennessee), boosting sales fivefold to 1,939 units and beating out the Volt in the process. That more than offset a 32-percent drop in C-Max Hybrid sales and pushed Ford's green-car sales up 15 percent to 8,879 units.

As for lower-volume green-car makers, Audi quadrupled its diesel sales to 1,692 units; Mitsubishi i battery-electric sales fell 44 percent to just 22 units; Porsche hybrid sales fell 41 percent to 367 units; Daimler unit Smart moved 358 of its ForTwo ED electrics; and BMW sold 358 of its i3 plug-ins during that model's second full month of US sales.