You could say 130 kph ( instead of 80 mph ) and we would understand. Again , absolutely not about FE or hypermiling stuff , but I drove an early 90s Nissan Pathfinder on I-94 in Michigan. Mostly around 100 MPH. At the SLIGHTEST hill , it would downshift a gear to maintain about 95 MPH. This might be specific to cars with approx. 100 HP. But I have only owned automatic cars since 2008 , so maybe I'm wrong. My 08 Civic would downshift to 4th or even 3rd in the mountains around Flagstaff , but I wasn't going more than about 65 MPH.