More U.S. drivers are springing for premium gasoline, and part of the trend has nothing to do with oil’s slump. Though gas prices have dipped to the lowest levels since 2009, automakers are also making fundamental changes to how cars run. Those changes, according to a recent government analysis, will have “widespread implications” for future fuel markets.

Pushing the higher octane button at the pump no longer necessarily means you’re driving a luxury car. New versions of the Honda Civic, smart fortwo, MINI Cooper, and other affordable models either require or recommend premium. Stricter fuel economy standards meant to reduce greenhouse gas emissions are driving big shifts toward auto designs that favor the more expensive fuel—at the same time,