The Numbers Don't Add Up...
For a long time, GM has been saying that there was no need to suffer from 'range anxiety' with the Volt because once the battery is drained (after anywhere between 25 and 50 miles), the car can go an extra 300 miles with the gasoline engine. But until now, the size of the Volt's gas tank was kept secret, so we couldn't estimate what kind of MPG the plug-in hybrid would get in gas mode. The only information we had came from GM chief engineer Andrew Farah, who said that the Volt would get about 50 MPG in gas mode. But now the size of the gas tank of the Volt is out...
According to Lyle Dennis, a member of the Volt's Consumer Advisory Board, the Volt's gasoline tank can hold 9.3 gallons, a number that he said he was able to confirm (I assume from someone at GM, but for now GM is just saying "no comments").
What this means, if you do the math, is that the Volt when operating in gas-only mode should be getting about 32.26 MPG (300 miles divided by 9.3 gallons). This is significantly lower than the 50 MPG target that Mr. Farah disclosed a few months ago.
This is a bit of a letdown because the Volt can use most of the fuel-saving techniques used by hybrid cars like the Prius; it can use regenerative braking, stop the gas engine when the car stops moving, and it can keep the engine at the RPM that provides maximum thermal efficiency. On top of that, the Volt was designed to have a low coefficient of drag and it will no doubt have low rolling-resistance tires.
Is the relatively low MPG caused by the extra weight of the batteries or is there something else we're missing? Maybe the 300 miles gasoline range number a very conservative estimate? We should find out fairly soon when people start doing more in depth reviews of the Volt, but in the meantime, GM should really give some clarifications.