I've just switched from first click to second click with the Jeep. Haven't had enough fillups to tell if it reduces variance. With the motorcycle, I just fill until gas is hits the bottom of the neck. Can't wait until the nozzle clicks off, it'll spray me with gas first. If I shoved the nozzle all the way in, it would probably cut the capacity in half
Fillup technique definitely matters, I get a lot variation on my trips thru OR, where you can't pump your own gas. I try to tell the gas station attendants not to top me off, but I think some of them do it automatically. Glad I don't live their anymore, its a bit frustrating not to be able to control the fillup when your tracking mileage.