MPG is linear. What isn’t linear is actual gas savings vs percentage improvement.
doubling the mpg from 10 to 20 saves 750 gallons a year at 15k miles. Doubling from 25 to 50 only saves 300.
Yep, it's just harder for non-analytical types to understand since it's really an inverse. People have trouble understanding when a higher number is actually a smaller amount of usage.
Using the Canadian version of L/100kM (or whatever function they use) is actually easier for most people to understand. Gallons per 100 miles would be easier for most people.
This morning's gas prices in Hamden, CT (New Haven)
$3.65 Regular (Cash) @ Gulf
$3.65 Regular (Cash) @ Citgo
Gulf is the usual price leader but since last week the Citgo station's prices have gotten very aggressive with a substantial advantage for Mid-Grade and Premium.
But here lies the rub, MPG is a terrible way of measuring fuel economy because it doesn't linearly scale
http://www.mpgillusion.com/p/what-is-mpg-illusion.html
The difference is that the Volt's ICE was also tied into the driveline, so it wasn't just a generator, which means it had to work harder at highway speeds, not just spend more time running.