Just How Dirty Are Our Classic Cars?

We need to clear the air (so to speak) about our beloved old cars and their impact on the environment. Granted, we drive them so few miles these days that any environmental impact is minimal. Some would argue that emissions from old cars is essentially insignificant when contrasted to all other forms of environmental polluters. I would agree in principle - provided the old car in question is well maintained - but we need to put all this in perspective by making a real-world comparison.

To do so, let's grab the keys to a fully-restored 1967 Corvette and a brand new 2004 Corvette and drive them enough miles to equal a specific amount of emissions output. Put another way; how many miles does the '04 Vette have to go to chalk up the amount of pollutants the '67 belches in a one-way trip from, say, Washington DC to Baltimore MD - exactly 42.32 miles from the Capitol building to the Inner Harbor. Place your bets, please...

The two major pollutants in gasoline are: volatile organic compounds (VOC's) and oxides of nitrogen (NOx). The other major gas streaming out of exhausts is carbon dioxide, a greenhouse gas. We're not going to count it in this exercise since it really isn't a "pollutant" (we exhale CO2 with every breath, so we're just as guilty as the machine.)

In 1967 federal pollution standards for VOC's allowed a maximum of 10.6 grams per mile. NOx standards allowed a maximum of 4.1 grams per mile. Driving our '67 Corvette from DC to Baltimore would, therefore, produce 10.6 X 42.32 = 448.59 grams of VOC's, which is nearly one pound. As for NOx, the '67 would produce 4.1 X 42.32 = 173.51 grams, or .38 pounds. Hmmmm...

Now it's time to drive our '04 Corvette. Its engine is allowed only .075 grams per mile of VOC's and .05 grams per mile of NOx (that's a reduction of 99.29% and 98.78%, respectively) so we're going to have to drive the car considerably farther.

How far? It doesn't take a mathematician to figure out we're going to have to drive the new Vette 5,981 miles to equal the VOC figure; a drive equal to a trip from the Capitol building to LA International Airport and back (5367 miles) plus a quick side-trip to New York's Central Park and back! As for NOx, we only (only?) have to drive the car 3,470 miles to equal the numbers of the old Corvette's trip to Baltimore. Therefore, we could stop driving on the return trip from LA around St. Louis.

And what about those gas-guzzling SUVs? The fact that they are gas-guzzlers doesn't matter, because pollution is measured in grams per mile. Therefore, SUV engines have to be clean enough to meet the federal standards (for 2004 the VOC standard is the same as for passenger cars and the NOx standard is .07, just .02 more than for cars) even though they are burning more fuel per mile. The plain truth of the matter is that we can drive an '04 Chevy Tahoe the same number of miles as the new Corvette before we equal the '67 Corvette's VOC's. It can go for 2,478 miles before equaling the NOx, and that's not too shabby.

This little exercise proves just how much cleaner today's cars are (141 times cleaner, actually!) than those of the 1960s and earlier. The fact is, automobiles really did pollute our atmosphere throughout most of the 20th Century, but the combination of regulation and creativity on the part of manufacturers has largely eliminated the problem.

Putting all this into context, those of us owning old cars owe a certain obligation to society to maintain them as close as possible to optimum running condition. Further, we should limit our driving to occasional use, something most of us already do.