EPA Butchers Chevy Volt MPG Rating

The EPA recently tested the new Chevy Volt, the car that has been advertised as getting 230 miles per gallon.  What the EPA came up with is a rather shocking 48 miles per gallon.  How did this happen?  The EPA simply changed the rules of their test in order to artificially lower the fuel mileage.  They did this by making sure that the car’s engine was running the entire time during the test - something the Volt is not designed to do under normal operations.

The Volt is a plug-in electric car with a backup engine to charge the batteries when they get low.  The engine is not connected in any way to the car’s drivetrain.  The EPA discovered that under normal testing the car did not need to engage its engine in roughly 85 percent of their tests, apparently they were not happy with that.  What this shows is that the EPA needs a new rating system to handle cars like the Volt, cars that do not run under a constant gasoline power source.  Even the fact that when they ran their tests while the car was allowed to run under electric power they still came up with roughly 100MPG is a little strange.  How do we account for the discrepancy with GM’s original claim of 230?

With any plug-in car, it all depends on the distance you travel.  For instance if I were to start my day with the car plugged in, drive to work and to a few other places in my day I might squeak past 50 miles or so.  With the EPA’s ratings one might expect that I had now used a full gallon of gas at 48MPG, but they would be wrong.  In fact I would have driven the first 40 miles on pure electric, not engaging the engine at all, the last 10 miles would have also been under electric but the engine would have been turned on pushing electricity to the batteries.  We will assume that the fuel mileage at that point is 48MPG.  Running 10 miles at 48 MPG means I would have used up a measly .21 gallons of fuel.  Driving 50 miles on .21 gallons of gasoline works out to 238MPG.  The number goes down the further you drive, for instance if you were to drive 60 miles in a day your MPG rating goes down to 146.  Drive less than 40 miles and you’ve used no fuel.

The EPA ratings system needs to be updated to account for these new types of vehicles.  This is the Motor Trend article I referenced.