I stay 2-3 seconds back. The "2 second rule" is the standard.
We were going out for a chore tonight and my boyfriend was about 3 car lengths back from the car in front of us, as we were going 38. He was annoyed that the guy was going "under 40" (with a speed limit of 40). I was annoyed that he was tailgating. He said he wasn't, and I said I'd look it up when we got home.
It looks like they say one car length for every 5 mph - meaning it should have been 8 car lengths back. He still says he was 2 seconds back, but it seemed pretty clear to me that we were NOT 2 seconds back.
So now his claim is he's never been in a bad accident so therefore his driving must be ok

This from the man who drives with his knees so he can eat a Blizzard with two hands ...
I guess what I should be doing is doing the driving when we drive together, if I feel this way!