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Why Those EPA Mileage Estimates Do Not Add Up

Prairie Eco-Thrifter

Gasoline Purity. No, gas stations are not selling dirty gas, but some gasoline varieties are cut with more ethanol than others. Burning gasoline that contains 10 percent ethanol (known as E10) will lower your fuel efficiency by up to 3-4 percent according to the EPA. The weather will rob your fuel economy as well. Maintenance.