I leave about one car length for every 10 mph between me and the car in front of me. I was wondering if this formula had changed
Yep, it's not the number of car lengths now it's two seconds. On clear, dry roads you need to stay two seconds behind the car if front of you. The faster you go the longer the distance that must be left to make two seconds. It's pretty easy to pick a spot on the road such as a road marker or tree and count one-thousand-one, one-thousand-two. If you pass the same spot before you get to two you're too close. On slick roads increase the seconds you count accordingly.
Two second rule.