Hey news, junkies Kansas trucker. I 10 west of San Antonio to El Paso which is 540 miles away is 85 for cars. 80 for trucks. San Antonio to Austin on a Turnpike. It's 85 80 for truck. I got my truck. I rode around 82 miles an hour in my truck big truck. I got scared back down. That's what it is out there. Also up in Montana is 80 miles an hour.