Plotting the efficiency of a commute

I've got a pretty good idea what kind of gas mileage Turbo Schlock (my 2003 GLS Turbo Beetle) gets. It's around 28 on the highway, and 22 in town. There are two routes to Dragon's Keep from my house that take about the same amount of time. One involves 3 miles of town traffic and 6.6 miles of freeway traffic. The other involves 6.6 miles of town traffic. It SHOULD be a no-brainer -- take the shorter route, and save on gas money. But let's do the math: 3 miles divided by 22mpg = .13636(r) gallons of gas. 6.6 miles divided by 28mpg =.236 gallons of gas. The freeway trip will therefore take around .37 gallons of gasoline. A round trip (assuming the same distance each way, which is close enough, even though the Center Street freeway access is at least a quarter mile longer in one direction) will take .74 gallons of gas, or almost three-quarters of a gallon. 6.6 miles divided by 22mpg gives us .3 gallons of gas, which is the total for the State Street route. Round trip, .6 gallons, for a savings of .14 gallons of gas over the freeway round trip route. So I'll keep driving on State Street. I don't get to go nearly as fast, and some of the traffic is frustrating, but I'm saving about 30 cents each time I do it that way. (then again... I have to ask whether saving 30 cents is worth the frustration...) I'm such a geek. --Howard