If you mean accelerate electric only up to 42MPH, it's very difficult. The computer makes it hard on purpose, accelerating with electric gives poor mileage since the engine is better suited to the task, in most cases. If your engine is warm and your battery has a good state of charge (SOC) but not too hot, not drawing a lot of juice otherwise (no AC or defroster) and you're not going up a hill (downhill is better) and you're VERY gentle, it might let you. If your battery is green it will use the battery far more often, trying to get rid of some excess charge. On the flip side, it's not prone to having the battery green, either! The system is more apt to let you accelerate with the engine to speed, then cruise with electric. Even then, at 42MPH it'll look for any excuse to restart the engine. While it may seem frustrating, the software is designed to maximize mileage and only use electric in situations where the engine isn't efficient, since EV mode has a lot of conversion losses to overcome. The EV mode button lets you be a little more aggressive in acceleration and other conditions, but has a lower top speed and other than a few instances, can result in lower MPG.
yup read the article evan posted. you're mainly still in the break-in period, and probably still 'learning' the different prius driving techniques. personally, i get 45-47mpg (sometimes less), mainly from 10-15minute trips to work in a hilly neighborhood with lots of stop signs. but when i travel for more than 30minutes, especially on the freeway at 60mph, i get a reading of 50-55mpg. (which is why i have more roadtrips :mrgreen: ). also, tire pressure does play a role in the mpg you'll get so check it regularly. may the mileage be with you! 8)
