The following was published in the Biddeford-Saco?Journal Tribune Sunday edition, 10/4/2015.

Just about every two weeks, for the past three years, Ive gassed up my car. On the printed receipt from the pump, I write down the mileage from the trip odometer before I reset it. Every few months, I take all the receipts out of the Altoids tin I keep them in and enter them into a spreadsheet  gallons, price per gallon, location of fill-up, miles driven  and use it to calculate my average miles per gallon, and where the reliably cheapest gas is. Embarrassingly, Ive even graphed the ebbs and flows of my refueling fun.

What can I say? I like math; I like numbers.

My arithmetical obsession has given me some insight into the inner workings of my car. My fuel efficiency always decreases in the winter, or when I set my cruise control at 79 miles per hour instead of 74. I knew something was wrong in July 2014 when my miles per gallon dropped from an average of 42 to 35. Turns out, my car had a faulty gasket and was spilling fuel all over the road. Yes, I could tell by the smell, but it was gratifying to see confirmation, and the real cost of the problem, in the data.

Im not a scientist, but I like to act like one. (It helps to work at the science-based Wells Reserve at Laudholm, a bastion of long-term monitoring.) Scrupulous data collection, overriding curiosity  those scientific methods are keeping me going this week. Otherwise, Id just be a furious, incredulous, dejected owner of a soon-to-be-recalled 2012 Volkswagen Jetta.

True, my car isnt a GM vehicle with a deadly ignition switch, or an SUV with a bad rollover habit. But it is the car I bought on the promise that I could have my cake and eat it too: performance and power, plus clean air and polar bears.

I proudly call myself an environmentalist, if perhaps of the more pragmatic (read: selfish) type. When the opportunity came three years ago to buy my first new car since 2000, I shopped around. I read reports. I test drove a Prius, some hybrids, a subcompact. And then I got behind the wheel of a bright red diesel Jetta, and I was sold.

Of course, I did the math. Diesel was, at the time, fifteen percent more expensive than regular unleaded, but from the manufacturers sticker, and later my own records, it was clear that I was getting 25% better fuel economy. Win! And the new Volkswagen TDI engines werent the snorting, belching, winter-hating diesels of old; they were clean diesels. I was as righteous as a Prius owner, but with a tachometer in place of a halo.

The story of how an auto testing laboratory at West Virginia University discovered the mismatch between Volkswagens on-road versus in-the-lab diesel emissions is a story of data and deduction. How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth? said Sherlock to his Watson. WVU research assistant professor Arvind Thiruvengadam and his team eliminated all the other explanations (incorrect readings, biased tests, faulty instruments) and, ultimately, were left with an improbable but true explanation: a global corporate conspiracy to bury a cheat in an onboard computer.

It was a multibillion dollar crime, one that perhaps even killed some people, with me and eleven million others as unwilling accomplices. A recall is coming. Some months from now, Ill have to bring my Jetta in for a lobotomy. It will emerge a slower, less efficient, less NOxious beast. It may lumber up the Casco Bay Bridge on-ramp, where it once roared.

By that point, I will likely be sorting through class action lawsuits to miserably join. But I will also be waiting to see what the data from my gas pump receipts reveal, because I like math, and I like numbers. Unlike car manufacturers, numbers dont lie.

?

Nik Charov is president of Laudholm Trust, the nonprofit partner of the Wells National Estuarine Research Reserve in Wells, Maine. His Sunday column, Between Two Worlds, ventures forth from the intersection of art and science, past and future, MPG and RPM. More at wellsreserve.org/twoworlds.