Driving in the pouring rain on hills and turns I was able to get about 18mph hwy on the way up. On the way down it was sunny and dry. I was not driving a steady 66/67mpg, running the car and did at least 12 pulls though was able to get 18.2mpg. This means that me that the weather had a profound effect. Perhaps the fuel at Chevron was better as well? Driving steady I could have obtained at least 20.5mpg(350x17)hwy!