Because it’s the first day of the Spare the Air program, as faithfully reported by yours truly, I’m going to have to set aside my journalistic objectivity and put in a plug for transit. Mind you, I’m a lover of the open road as much as the next red-blooded American, but this is about civic duty and, more to the point, our financial and psychological self-interest.

This is not, however, about the delicious grilled chicken and tuna, mashed potatoes and corn-on-the cob served up at the Spare the Air kickoff on Treasure Island yesterday. I joined my colleagues from the transportation media in swearing an oath before chowing down to never cut the sponsors, the Bay Area Air Quality Management District and the Metropolitan Transportation Commission, any breaks whatsoever.

This is not about favoritism, it’s about math, which I did with the help of my handy cell-phone calculator on the Capitol Corridor train this morning.

I live in the Central Valley, and some very smart people think I’m insane for commuting to Oakland every day. (note to Bike Mafia: I rode to the train station this morning). Amtrak, which operates the line for the multi-county Capitol Corridor authority, charges me $255 a month for my 70-minute ride. Because I need a car at work, I have to drive at least twice a week, so that leaves me with 35 train trips for the month of June.

Now suppose I drove those 35, 67-mile trips. Assuming, generously, that my 6-year-old Honda Civic will deliver 30 miles to the gallon, that means I would need 78.2 gallons for the month. How much are you paying for gas these days? My average has been running around $3.20 during recent weeks. At that price, I can expect to pay $251 for gas, to say nothing of the repairs I’ll need to keep up such a lengthy commute.

Chances are, you don’t get such gas mileage, especially sitting in traffic, waiting for the Bay Bridge toll booths. You probably don’t have to travel as many miles, either.

But just for fun, do the math. Figure out how much you’re paying for gas, and how much transit would cost. If your employer offers Commuter Check, also figure in the tax savings. I get the maximum I can, $110 a month, and my employer, the MediaNews Group contributes nearly a third of that. The rest is income-tax-free, so I save about $50 a month, which almost pays for the BART fare that gets me from Amtrak to my office.

If you do those calculations, you may find that with today’s gas prices, especially those on the Peninsula, along with other car costs such as parking and maintenance, that transit is a wash at worse. If you don’t need your car at work and commute by transit the full 44 trips in June, it could be that a monthly pass would be an even better deal.

Sure, it would be nice if every day was a Spare the Air, free bus and rail day, but they aren’t. Even with government subsidies, transit still costs, but thanks to soaring oil prices, those fares no longer look so exorbitant.