According to the April issue of Consumer Reports, the 4 cylinder and the 6 cylinder Sienna minivans both get about the same mileage, but the 4 cylinder is considerably slower. I have a 2011 Sienna V-6 that I purchased just after they came out in March of 2010. My mileage runs 16-18 around town and 23-25 on the road. For highway travel, I think you will find the V-6 quieter than the 4. I have about 16,000 miles on my Sienna and have had no problems at all. Since my other vehicle is a 2003 Toyota 4Runner, I was considered a loyal Toyota driver and have free oil changes for 2 years. I have had no expenses other than gasoline.