I did a 2,000 mile trip over the Rockies last summer, did the Coca Cola highway at 100 mph, the overdrive gear in the TKO 600 made that speed enjoyable. Just glad I didn't get the car impounded for excessive speed. That KPH to MPH gets me in trouble once in awhile. Averaged around 22 MPG as well. Another 500,000 miles and the savings in gas will have the tranmission paid for.