I bought a Mazda3 in early May. My last tank that was mainly freewway driving with some suburb with stop lights was 38MPG. With more city type driving I get 34 overall. So a 20 to 30% gain from there would be about 42mpg combined hightway and city driving. A lot of energy is lost shipping over the main lines and like 50% of the total shipped is lost going from the power company to the main lines to you house. Plus, look at the new batteries for Apple's new EV, OMG>>>>