However, diesel contains 11% more energy per volume than gasoline. Also, due to the nature of the fuel, diesel engines can run at higher compression in its cylinders. The higher the compression in the engine, the more efficient the process. This is why diesel engines get better mile-per-gallon ratings than gasoline.
Diesel engines and gasoline engines also produce different tailpipe emissions. Burning gasoline, for example, produces more carbon dioxide (CO2) and carbon monoxide (CO) than diesel.
While diesel engines produce less CO2 overall, they release 15% more CO2 per volume of fuel than gasoline as well as 20 times as much mono-nitrous oxides (NOx) — a chemical that damages respiratory systems. To cut NOx, automakers developed a system called the Selective Catalytic Reduction (SCR), commonly referred to as a “urea treatment.” SCR converts NOx into diatomic nitrogen and water in the catalytic converter in the exhaust system.
While gasoline has long been the default fuel for Americans, diesel has been the fuel of choice in most of the world. Europe embraced diesels because efficiency trumped concerns of tailpipe emissions.
The German automotive industry’s infatuation with diesel engines stretches back decades, but it hit its stride with a new diesel engine technology called diesel turbocharged direct injection (TDI), pioneered by Volkswagen-owned Audi in the late 1980s. TDI engines injected diesel directly into the cylinders, which made startup easier and virtually eliminated the soot clouds that would envelop diesel cars of the past.
Though VW Group had TDI tech for years, it didn’t take the center stage of the company’s marketing and budgets until it made a big impact at a little race called Le Mans.
At the 2006 24 Hours of Le Mans — the most significant motor racing event in the world — Audi changed the face of the diesel market forever when it unveiled its diesel-powered R10 TDI Le Mans Prototype 1 (LMP1) race car. Leaning on the efficiency of diesel, Audi was able to make more laps of the roughly 8.5-mile Le Mans circuit per tank of diesel than its gasoline-burning competitors. Over the grueling 24-hour race, where the cars drive more than the equivalent of a road-trip from New York City to Los Angeles, a few extra laps is all it takes to win.Not only did Audi dare to enter — and win — the 2006 Le Mans with a diesel race car, the engine underneath its hood pushed the boundaries of what was considered possible with diesel. With the TDI engine, Audi created a strategic advantage, one that carried beyond the race track and into the consumer market as well. Taking home the Le Mans LMP1 trophy that year, Audi became the first carmaker to triumph in the illustrious race with a diesel engine. It also arguably set the VW Group on the path that has culminated in Dieselgate.
Success with TDI gave Audi more than a trophy. It gave the brand technological bragging rights and a reason to beat its chest over diesel. Audi’s TDI technology increased fuel-injection pressures beyond what some thought was even possible. Moreover, it won Le Mans with a diesel, a fuel other race teams thought impractical for elite motor racing due to the engine’s extra cost and heft.
Of course, pushing the limits of diesel injection technology was a financial burden for the Group. However, it was a burden that the VW hoped would pay for itself. The group leaned on racing research and development to further consumer car development. Audi doesn’t publicize its racing budget; however, some pegged it around $15 million in 2006.
Around that same time, in 2007, the U.S. government set average automaker fuel economy standards at 35 miles per gallon (mpg) by 2020. Meanwhile, global fuel prices were climbing to all-time highs. So investing in diesel engines to meet consumer and legislative demands for more efficient cars made good financial sense. After all, not only could VW Group garner headlines with its diesel-powered racing victories, it could amortize racing R&D costs across its brands by sending the tech into showrooms, satiating consumers and legislators alike. From both a branding and ecological perspective, it was a win-win.
With each passing year, the emphasis and investment in the company’s TDI engines grew. Between 2006 and 2014 Audi won Le Mans eight times — all with diesel technology under the hood. Each TDI engine was more advanced and efficient than the one before it. Accordingly, yearly racing budgets grew, ballooning to an estimated $242 million by 2014.
By then, the TDI technology developed for Le Mans had spread into many consumers cars in VW, Audi, and Porsche showrooms.
The diesel curse
Diesel quickly became part of a bigger plan for the VW Group. Rather than using it to simply meet and exceed fuel-economy standards, diesel engines would become a centerpiece of VW’s marketing, potentially attracting new customers, especially environmentally conscious ones. The trick would be to ensure those customers didn’t have to pay too high a premium for the privilege.
In the 2000s, while Audi was collecting Le Mans trophies with its TDI engines, the VW Group determined to become the world’s biggest car company. Along with growing global sales, it aimed to significantly improve sales in the world’s largest car market: The U.S.A. And it would rely on diesel to do so.
VW had already been selling diesel cars in the U.S. Its new TDI engines, though, were marketed as so-called “clean diesel,” because they supposedly ran as cleanly as gasoline engines while returning 33% better fuel economy.
TDI engines would be both easier on the planet as well as your wallet, as they could achieve upwards of 40 mpg on the highway while also meeting the U.S.’s stringent tailpipe emissions standards that the emitting of NOx at 0.05 grams per mile.
To cut the cost of urea-treatment systems in its mass-market cars, VW had a simple solution: It didn’t install them. Despite not including these expensive treatment components, during EPA laboratory testing the cars still managed to pass emissions standards.
It turns out, however, as we’ve learned over the last week, VW engineers had installed so-called “defeat devices” that could detect when a vehicle was in test mode versus normal driving mode. In order to meet tailpipe emissions regulations, when in test mode, the car would cut fuel to the engine. This would lower NOx emissions to below federally mandated levels while also significantly cutting performance. When out on the open road and no longer in test mode, the cars would return fuel levels to normal — along with performance — and emissions would skyrocket to as much as 40 times the legal limit.
The inevitable conclusion
While we don’t yet know exactly when or how the decision to cheat emissions tests manifested, the motivation is clear: Decision-makers within the company looked at fuel-economy standards, customer interest, emissions laws, and overall cost, and came to a similar conclusion as Honda.
Unlike Honda, however, VW had made enormous investments in diesel. One could argue its whole identity was wrapped up in the fuel.
So, in the face of a stark reality that it had made a bad bet, the company chose to fudge the numbers and hoped no one would notice.
A decade ago, VW Group made a gamble. It bet it could do something that everyone else thought was impossible — make diesel a winning fuel, on the race track and the road. But it was wrong. And rather than face the music, set the company back years in R&D and lose millions, Volkswagen decided to fake it.