The 3.6 V6 is an excellant engine. Our 300 gets 25-27 on the highway and 22-24 around town. It is not broke in at 4000 miles and will expect to get higher mileage as the engine becomes freer. I would recommend a 2013 model as it has the * speed transmission. This transmission makes the V6 come alive, the old Mercededs sourced 5 speed is alright but not world class like the 8 speed. Depending on the trim level the seats can be soft to firm just like the ride. We have the S model and the seats are comfortable for long drives.