Far fewer people have been refueling with high ethanol blends this year in parts of the Midwest.

In North Dakota, sales of E85 — gasoline blended with 85 percent ethanol — were down by more than 60 percent this year from January to May, compared with a year earlier, according to the state’s Commerce Department.

Minnesota has also experienced a severe dip in E85 sales, according to The Star Tribune in Minneapolis. Around 1.5 million gallons were sold in May — which is almost 1 million less than a year earlier, the paper reports.

Because ethanol has a lower energy content than gasoline, ideally it should be priced 15 to 20 percent lower than regular unleaded to make it worthwhile on a cost-for-energy basis, Mr. Lambert said. Consumers, he said, should “never, ever, ever buy E85 when it is priced higher than gasoline.”

But the price was higher, at least briefly, in Iowa, according to Monte Shaw, the executive director of the Iowa Renewable Fuels Association, in the wake of plunging gasoline prices last year.