Hi,
I have reached 30mpg driving my gs430 over last 2500 miles during the trip through Europe few weeks ago. I have notice just about 1mpg difference in consumption when driving between 80 and 110mph. Petrol used 98 and 105 on Aral station in Germany. There was about 40 eurocents difference in the price but I think it wasn't worth the price. On the tank maximum range 380 miles, but it happened once. Usually on the motorway after refilling 350mile on the computer is shown.