Shale oil, which the Energy Information Administration projects will represent a rising proportion of American oil supplies in the coming decades, has a surprising Achilles heel: its low octane levels, which make it a poor fit for the high-efficiency car engines of the future. For financially troubled shale drillers , that’s bad news, since it suggests demand for their oil could fall even if the price of a higher-octane oil barrel rises. For the rest of the country, shale oil’s quality issues raise important questions about whether building infrastructure to support decades of shale oil production is smart public policy, because a shale oil boom could ironically spell higher prices at the gas pump for American drivers. Or if shale oil makes regular but not premium gas cheap, that could deter Americans from buying premium-fueled cars despite better gas mileage, undermining plans to cut tailpipe pollution by building better […]