It's engrained in my siblings (we all had the same dad, after all.Growing up, my parents always kept a record of when they filled up; gallons and cost. Why? I know my dad would calculate MPG but only saw him do that on trips. I don't think they do this anymore. Drove with my dad 700 miles a few months ago and I did not see him record the info. I started doing this when I first started to drive since that is how I grew up. Gave it up in a few years.