The U.S. average retail diesel price slipped 0.3 cent to $2.423, the Department of Energy said as the price of crude oil continued to wobble below $50 a barrel.

U.S. trailer orders fell 12% in May, reflecting typical seasonal demand, ACT Research Co. reported — though trailer manufacturers said the market had softened.

California has expanded its testing of zero-emissions electric-powered heavy-duty vehicles as the state grapples with finding solutions to the worst air quality in the nation in several of its cities, experts said.

The U.S. retail diesel average climbed 2.4 cents to $2.431, the Department of Energy reported, while the volatile price of crude oil slipped below $50 per barrel.

Class 8 truck orders in May plunged 30% year-over-year, two research firms said, underscoring two truck manufacturers’ recently announced plans to trim production for the second time this year.

The U.S. retail diesel average climbed 2.5 cents to $2.407, the Department of Energy said, increasing for the 15th time in 16 weeks as crude oil flirted with $50 per barrel.

The price of a used Class 8 truck sold in April fell compared with a year earlier, but inventories stabilized after rising for the past year, analysts said.