After filling up, my numbers start at around 5 or 6 mpg and climb up from there. After about 15-20 miles the numbers level off and stabilize at realistic values.
During winter when I'd wait in line for the car wash after filling up, they'd start at 5 and go down from there, think the lowest I was 2 mpg.
During winter when I'd wait in line for the car wash after filling up, they'd start at 5 and go down from there, think the lowest I was 2 mpg.