The rush by Americans to buy smaller, more fuel-efficient vehicles hit a speed bump in May, Reuters reported.

The rush for vehicles with higher gas mileage is more restrained than three years ago and is beginning to fade, even as gasoline prices test their 2008 peaks and automakers tout an expanded lineup of gas-sipping vehicles, from plug-in cars to six-cylinder pickup trucks, according to data compiled for Reuters.

In May, the average fuel economy of new U.S. light vehicles fell for a second consecutive month to the lowest point since January, according to online auto-buying research website TrueCar.com, which compiled the data for Reuters.

That means that since January, average mileage has risen by just 1.4 percent to 21.9 miles per gallon; over the same period in 2008, it jumped by 6 percent to 21.2 mpg, Reuters said.

“By November of 2008, everybody had already gotten over $4 a gallon and were back to their old ways. It was a panic situation; people overreacted,” AutoNation Inc. CEO Mike Jackson said. “People now feel they’ve already seen the movie. They’ve adjusted to it.”

The price at which most car buyers would begin panicking and adjusting their buying behavior — what Jackson calls the “freak-out number” — has moved to $5 a gallon from $4, Reuters said.