Even though gas prices are nearing $4 a gallon, ethanol is helping drivers across the country save an average of $156 per year.

That’s according to the Renewable Fuels Now (RFN) coalition and a recent Iowa State University study calculating ethanol’s impact on gasoline prices around the country. The study concluded that, by expanding the fuel supply, ethanol has made gas cheaper by 29 cents a gallon to as much as 40 cents a gallon.

RFN considered Federal Highway Administration figures on vehicle fuel efficiency and average miles driven per year to extrapolate average yearly savings thanks to ethanol in different regions of the country. They found that on the east and west coasts, where gas prices are especially high, drivers are saving an average of $142 a year on regular unleaded. In the Midwest, they are saving $241 a year.

Savings are lowest in the Rocky Mountain region, but motorists there still save as much as $104.52 per year, according to the study. On the Gulf Coast, the savings are over $150 per year.

According to a detailed breakdown by vehicle type and region, some drivers could save over $280 per year.