I bought a new Sienna CE on February 27, 2004. I drove home from the dealer, 70 miles, filled the tank brim full and drove 597.5 road miles before a complete fill up of 20.4 gallons, which equates to 29.289 mpg. I was ecstatic that a brand new vehicle could get that kind of gas mileage, especially considering that first tank of gas was from a Dallas area station which is in an EPA non attainment area which means the gas has additional additives which usually lower gas mileage. HOWEVER, since that time, my road mileage has run from around 21.8 to a best of 27.04. These two extreme readings occurred in December 2004 and January 2005 on the same stretch of I-20 east of Dallas, not using the air conditioner and under similar driving conditions and weather. The original sticker on the window stated that road mileage for a V6, 3.3 L engine should run 16-22 mpg in the city and 22-32 mpg on the highway, with average readings 19 mpg city and 27 mpg highway. My city driving which is mostly freeway has never been better than 21 mpg and is usually 18-19 mpg. This is my road vehicle and is rarely used in town. Previously, I owned 4 Camrys, 1995, 1996, 1998, and 2004 models, and consistently got better road gas mileage than the EPA ratings. I am very disappointed with the Sienna's performance and the engine seems undersized. It downshifts from overdrive on most small hills and has to wind up just to get on a freeway. By comparison, I have a 1998 Windstar which I drive the heck out of, no babying along like I do the Sienna. The Windstar has over 187, 400 miles on it, has a 3.8L V6 and is very strong. I drive it back and forth to Dallas and usually get 22-24 mpg, compared to 18-19 mpg on the Sienna on the same stretch of interstate I-35E. The dealer has had the Sienna twice and says everything is within spec. I noticed on the 2005 models with the same engine that Toyota has lowered the mileage estimates to 19-26.
ANYONE have any comments or suggestions?