Volt's multiple MPGe ratings explained

GM releases a video to explain the EPA's multiple MPG-equivalent ratings for the Volt, which launched in the U.S. last week.

2011 Chevrolet Volt gets 69 MPGe if you recharge its battery ever 75 miles, according to the EPA's new ratings system. GM

General Motors has turned to YouTube to explain the EPA's new ratings system for alternative fuel cars, particularly for its new Volt.

Earlier this year, the Environmental Protection Agency revamped its car rating system to offer MPGe (miles per gallon equivalent) ratings.

It's a tool for comparing alternative fuel vehicles and hybrids to cars with gas-only combustion engines. So while a car may use electricity alone--as with the Nissan Think--the EPA still calculates an energy-equivalent consumption comparable to a gas-engine car.

The hybrid electric Chevy Volt, which was released in the U.S. last week, presents a particularly unique challenge to rate because GM developed an extended-range hybrid drive train that essentially allows the car to run on electricity alone for its first 35 miles after which a gas-engine kicks in full time. The Volt's complex system uses the car's gas engine mostly as a generator to power the car's electric drive train, but it also drives power directly to the wheels when going over 70 miles per hour.

If a driver recharges a Volt's battery every 35 miles and runs the car on electricity alone, the Volt gets 93 MPGe. On gas alone, the car gets 37 MPGe. But the EPA also combines ratings for real-life use depending on how often the driver recharges the battery.

So unlike the all-electric Nissan Leaf or Toyota Prius which received MPGe ratings for city, highway and combined driving, the Chevy Volt label has multiple ratings allowing for various recharging scenarios. If the car is recharged every 75 miles, for example, it gets 69 MPGe.

Below is GM's video, which showed up on YouTube yesterday:

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