Actually, using mm to recharge is not that inefficient if you run in on the highway and use the charge to drive around in the city. Once I had a depleted battery and ran mm mode on the highway for about 20 miles. I noticed that I was getting about 20 mpg during that portion. I was also able to get almost another 20 miles of low speed driving in the city from that charge. That's about 40 mpg. The volt is great when using the battery, but it''s annoying when running on gas in the city. The engine is constantly cycling on and off at a very high rpm, so it noticeable and loud. My old Prius was much better for running around town using gas. The Volt is a great car, but its weakness is running on gas in the city or in the hills. It feels underpowered when climbing hills.I would not recommend using mountain mode for anything but mountains. Using the generator to recharge the battery is inefficient and unnecessary.