Cheapest Gasoline Ever?

Last week the Energy Information Administration  (EIA) reported that the $2.43 per gallon average US retail price for regular gasoline in 2015 was the lowest since 2009. A quick look at the EIA's handy page for comparing nominal and real fuel prices over time shows that last year's average, when adjusted for inflation, was actually the cheapest since 2004. A recent article suggested that current prices are lower than those in the mid-1960s, in the heyday of the American love affair with driving. I've lost the link, but that factoid checks out, too. However, even this understates the bargain currently on offer at the gas pump.

The price of gasoline is still one of the most visible prices in the US, prominently displayed on gas station signage and roadside billboards across the country. However, it only captures one aspect of how much motorists really pay, just as measuring fuel economy in miles per gallon misses the economic impact of driving. A few years ago I ran across a metric that combines these factors into a simple gauge of driving cost: miles per dollar, or mp$.

The chart below incorporates EIA data on inflation-adjusted fuel cost and data from the National Highway Transportation Safety Agency (NHTSA) on actual fleet corporate average fuel economy (CAFE) performance for each model year of passenger cars--not SUVs or light trucks--to display average mp$ for the last four decades.

Taking last week's average price of $2.03 for unleaded regular and using 36.4 mpg for the 2013 model year (the latest on NHTSA's site), today's fuel cost of driving is cheaper than at any time since 1978--and maybe ever. The 18 miles per dollar I calculated just beats the previous peak of mp$ in the late 1990s, when fuel economy was around 28 mpg and gas prices averaged barely over $1, due to the effects of the Asian Economic Crisis. By comparison, the $0.31 per gallon that motorists paid in 1965 was downright expensive, after adjusting for inflation and factoring in the low-to-mid-teens fuel economy of cars of the day.

Miles per dollar is also handy for comparing driving cost on gasoline to the cost of operating vehicles that use other fuels or electricity. When I first looked at miles per dollar in 2008, electric vehicles were significantly cheaper, per mile driven, than cars running on gasoline or diesel, even hybrid cars like the Prius. That gap still exists, but it has narrowed. At an US average residential electricity price of $0.126/kilowatt-hour last year, a Nissan Leaf or Chevrolet Volt would get around 26 mp$. However, in New England and other parts of the country with significantly higher-than-average electricity prices, the miles of driving that an EV can deliver per dollar of energy used could be less than that for gasoline in some locations.

A few caveats are in order. Based on data from the Transportation Research Institute at the University of Michigan, new-car fuel economy has slipped 0.8 mpg since oil prices started falling in the summer of 2014. And in any case, new cars are typically more efficient than the entire US car fleet, which includes older vehicles and substantial numbers of SUVs and light trucks. The Consumer Price Index is also an imperfect tool for comparing prices over long periods of time, because the Bureau of Labor Statistics periodically changes the components of the "basket" of goods and services that go into calculating the CPI.

None of those issues seems big enough to alter the basic conclusion that the gasoline cost of driving is exceptionally, perhaps historically cheap at the moment. If oil prices stay "lower for longer", as some experts expect,  changing the make-up--and thus the emissions--of the US car fleet is likely to be an uphill battle.