Random guy at a Denver bus stop told me to check my tire pressure when it gets cold, and it fixed my gas mileage
I was complaining to a stranger at the stop on Colfax about burning through a full tank in under a week and he said cold air drops tire pressure about 1 PSI per 10 degrees, which I never knew. Topped all four up to 35 and my next tank lasted 40 extra miles. Anyone else learn a basic car thing from a total stranger?