Yes deedee you can use regular gas. I've got a dozen or so tanks through mine and it does just fine.

As for the mileage if you search P&G and PnG you will find a variety of threads on the subject. It really isn't about using the battery though. The stuff I've read attempts to use the battery as little as possible. It is a 40-45 miles per hour speed limit technique that can produce 40+ mpg on a HiHy.

As in many other threads, tire pressure is critical and short trips are mileage killers.

Nellaroo, if you are letting the vehicle sit and warm up so the engine shuts off for driving at low speed, the warm up will hurt mileage as well.