True...but only if GALLONS of gas are the only fuel used!
With Volt, the first 40 miles they use in this equation are "cheated" from charging plugged in overnight.
Ok, sure. If we want to play this way, then the EV-1 electric-only vehicle got INFINITE MPGs!
I think some kind of new metric beyond MPG is going to have to be created for these serial hybrids, and of course, all-electrics as they begin to show up.
If for nothing else, for efficiency comparison. If they up the battery capacity to 45 miles, then by this current definition, you only burn
MPG = M / G = 230 = 50 / G ... G = 50/230
So this 50 miles test uses 0 gallons for 40 miles, then 0.217 gallons in the last 10 miles. That means, really, the gas engine is getting 46 MPG when it's running.
So suppose that they just increase the battery capacity to squeeze 45 miles out of it. Then you only use 0.1085 gallons in 50 miles, uh... 460 MPG!
See the problem? Eventually MPG has no relative meaning anymore. I would like to know how much the electricity charge costs really factor in overnight.
Let's guess it's a 15A/115V plug.
Let's use Chevy's number below that "8kWh will get you 40 miles."
Let's allow for the low electric prices and use $1 (btw, utilities add surcharges for fuel, so when gas goes up so will electricity.)
At $3 gal, let's just say 1/3 equivalent gallon. So let's say that's 120 Equivalent MPG. The average of those more real numbers is STILL 105.2MPG, which is very impressive and informative about the relative efficiency.
All of those numbers are true. As long as people understand what the number means, all is good.
There are only two real reasons for people to even care about a mpg number — how much will it cost me to drive ‘X’ miles, and how does it affect our need to buy oil from foreign sources.
Very little electricity is generated from foreign fuels, and the cost per mile for the all-electric miles driven is much less than the gasoline miles driven.
So I am happy to see the 230 mpg rating being advertised for the Volt.