User expectations: 230-MPG is DOA

So, with regen braking, low wind drag, and low rolling resistance tires, I would expect this thing to get a prius-like 50mpg with the ICE supplying power to the electric motors (not in pure EV mode).

But then you're lugging around 400lbs of batteries.

So maybe 40-45mpg when powered by the ICE?

 

On the highway, the weight has a relatively small impact, especially when not climbing much. In town, more important with repeated accelerations, but still not as big as you propose. Just my humble opinion.

 

One of the mysteries still surrounding the upcoming Chevrolet Volt is the size of its gas tank. Insiders have told GreenCarAdvisor - and we've reported on numerous occasions - that the extended-range electric vehicle will be fitted with a nine-gallon tank or something very close to that capacity. And when we spoke with General Motors spokesman Tom Wilkinson today, he said the automaker has still not officially disclosed the size of the tank, but that "it's somewhere in that [nine-gallon] neighborhood."
Regardless, a recent report by Eric Evarts of Consumers Reports stating that the model's fuel tank "will likely hold about nine gallons" has generated a lot of buzz on the Web today.
Various sites and blogs, including gm-volt.com, which does nothing but report on Volt developments (but is not affiliated with GM) went so far as to report this week that "the presence of a nine-gallon tank either means the range will be nearly 500 miles, well above previous promises, or that mpg in extended range is only in the low 30s."
AutoBlogGreen.com has taken the, uh, news, a step further, posting a blog today headlined: "Report: Volt gas tank holds 9 gallons, total range could be nearly 500 miles."
GM has stated for many months that the overall range of the Volt will be about 340 miles, including the approximately first 40 miles in pure electric mode.
We asked Wilkinson today about the nearly 500-mile range, and this was his response:
"We've said 340, including a fully charged battery. It may be a little conservative. Depending on driving cycles it can change a lot. If somebody's only doing city driving versus steady state-highway driving, there's a big difference.
"Until we've actually got official EPA numbers and official capacity for the tank that take into account the evaporative-emission requirements and everything, we'll stick with what we've got. We'd rather have people be pleasantly surprised that disappointed."
So despite all the speculation surrounding the Volt's mileage and, still, gasoline fuel capacity to run the motor-generator, GM is still saying Volt owners should expect to get about 340 miles with a fully charged battery and a full tank of gasoline.

"Chevy Volt to Go Nearly 500 Miles Fully Fueled? Not So Fast, GM Spokesman Says" Green Car Advisor