I recently (2 months ago) acquired a 2009 ex-leased Prius with 19k on the clock. I was very happy with my 35mpg (a vast improvement on my previous 13 yr old cars 18mpg) Until a Prius driving cab driver burst my bubble. He was getting 44mpg in stop and go Los Angeles traffic. This friendly cab driver suggested changing the engine air filter (I just ordered a new one on ebay) and changing the oil ( I don't remember which oil he suggested I change it to) So my question is, Is it worth getting an oil change? what kind of oil will make the improvement? Is there something that the previous driver was doing that has permanently reduced my MPG?, could there be a problem with the battery? I'm a newbie here with hybrids and do not drive vast distances, I never drive on the freeway and mostly drive distances of less than 20 miles.