https://www.consumerreports.org/cars/car-repair-maintenance/...
https://www.eia.gov/tools/faqs/faq.php?id=27&t=10
> The energy content of ethanol is about 33% less than pure gasoline. The impact of fuel ethanol on vehicle fuel economy varies depending on the amount of denaturant that is added to the ethanol. The energy content of denaturant is about equal to the energy content of pure gasoline. In general, vehicle fuel economy may decrease by about 3% when using E10 relative to gasoline that does not contain fuel ethanol.