Ah I noticed you must not OWN a volt yet, unless I knew that I would have access to electricity at some point in the future, from an economic standpoint it isn't worthwhile, but I don't think I can really justify any new car economically so you would have to decide for yourself if a $40k car is worth it to you as it is (aka for other reasons). A prius for gas only use is probably more "user friendly" and economical but my statements below still stand.
The volt is a bit off when it comes to calculating its real MPG when it runs on gas due to the extra EV range that is sometimes made. (especially the mountain mode ev range that doesn't always go to MPG)
Your situation is AN EXCELLENT opportunity to see how many real MPG your volt can get.
And be sure to report your tank to tank at ecomodder.com, many there would be interested.
If I owned a volt (and wasn't just a wannabe that drove one once) I would probably run on just gasoline for about a month to get the hypermiling technique down, get the motor broke in and to report on ecomodder.com with some real data.
Not to mention you might be the only volt owner on this site that will actually get his gas motor "worn in" enough to know the real fuel economy the volt is capable of. Also remember that if the volt motor can actually achieve operating temperature its FE goes up a lot, many here probably never get the motor warm and can never see this side.
As an example my cobalt took nearly 6k miles for my fuel economy average to move from high 30's to high 40's mpg wise as the motor broke in.
I would also use this opportunity to test pulse and glide volt style. Since you have a mountain mode button, you might try to selectively use that button to force the motor to run at its most fuel efficient per HP area when you are accelerating or going up a hill then shut off (switch to CS) and use the EV range it generates at stop lights, in town or even on the highway on and off. (on up hill, off down hill etc) Just like a hypermiler, except the speed up and down would be fully optional (but maybe beneficial) because of the magic of the volt.
Ecomodder.com has a BSFC chart for your volts motor, if you can figure out how and when it runs in the ideal RPM/power range (or close to it) you might find your volt is capable of a real and honest 50-80mpg at certain speeds driving a certain way (but only after you check tank MPG the old fashioned way with the odometer/trip meter and fillup info)
Anyway does the volt log gallons on the display? Never noticed if it did, but if it did you could know I traveled X miles and hid says I used X gallons just for a test.
The prius can be driven to nearly 100mpg by keeping the motor at its peak power (at variable low speeds), I have no doubt your superior volt can be driven to new heights as well if you have the right speed roads and patience.
Good luck and enjoy your opportunity to prove the ideot talkhead "on My volt testdrive I got 25mpg from the gas motor over .2 miles in -40 below weather" folks wrong.
Here is a small amount of inspiration.
http://ecomodder.com/forum/showthread.php/some-real-volt-numbers-curious-19370-7.html
And he isn't even a full on hypermiler by any stretch. 48-50mpg driven relatively normally.
You could also educate other people on how to drive in the sweet spot of the volt drivetrain like Wayne Gerdes did on the prius, this not only would help people to know how to hypermile in the ev mode but also help them to know what to do in the gas mode when they need to use it to get the best FE.
As far as I know, no one has mapped out the volts MPG VRS speed using its various modes and no one has calculated the # of gallons of fuel the volt motor in mountain mode uses to charge up the battery a given # of KW's. Ideally your motor should put all its effort into the EV motor and not into charging but you could find a min/max MPG based on these type of numbers. Also remember in CS your motor typically is not running at its peak rpm/efficiency so the efficiency gain from MM on both the genset and motor may offset the charging loss penalty.
Remember every situation is a chance to learn, make sure you have fun with the situation you have been handed, the voltec drivetrain really is still in its infancy at least from a code perspective, I believe there is a lot of gains to be had on the gas side of this interesting drivetrain that no one has fully explored.
Not to get too involved but you can provide real and usefull data to the whole community if you do this right.
Are you up to the challenge?
Thank You
Ryan May