Yes. I also keep a little record book in my glovebox, and record mileage, gallons, etc every time I buy gas. New tires, oil changes, etc go in the book, too. Driving from Virginia to Maryland, which I used to do on a regular basis, I would try alternative routes, and compare actual road miles to time traveled, in an effort to determine which way was more efficient. For a while, just for the hell of it, I experimented with finding the absolute shortest possible route, and kept trying different little country roads, shaving a mile here and a mile there...eventually got bored with it, as the back ways often took longer even though shorter distance.
At work, people will often ask or compare the cheapest gas stations they've seen recently...I always am the one who knows the cheapest; a place that is almost always about a nickle less than anywhere else in the area. Nobody wants to go there but me though, as they say it's too far. Immediately responded, "Oh no, it's only 5.1 miles, whereas the one you go to is 1.2 miles, which isn't that much difference, and worth the .05 x 12 gallons = .60 in my opinion. Got very strange looks..."You MEASURED IT?!!" Me: Well, yeah!