Has anyone documented a gas mileage increase from 0 miles to whatever you consider broken in on a new car/truck? Not asking for butt-dyno guestimates, actual calculated miles/gallons over the break-in period. I never have been able to confirm an increase maybe because I didn't have repeatable driving conditions. My dad drove 50k highway miles a year when he was working and kept meticulous records, new car every 2 years, and saw at best something in the low tenths, this with mostly GM cars up to 1990. StevieC, you drive a bunch, what have you seen?