auto maintenance January 11, 2018

I hate to say I told you so, but…

My father, a highly regarded auto industry journalist/analyst, always questioned the wisdom, viability, practicality, and the cost-benefit ratio of diesel cars. Europe had always been diesel heavy, but that was a result of tax policy rather than consumer preference. I agreed with him, and usually advised gasoline over diesel unless it was a truly truck truck that was going to do truck things.

But the exception was always Volkswagen, who seemed to have the diesel thing down in a way no other manufacturer did. When Volkswagen replaced its legendary unconventional Beetle with the equally unconventional Rabbit series in 1976, one of the many unique features was the availability of a diesel engine, which shared a common block (the main part of an engine containing the cylinders, pistons, and crankshaft) with the gasoline version of the car, greatly reducing the extra cost diesels entail.

The very first manual transmission I drove was a ‘77 Rabbit diesel that Dad brought home for testing. Not much performance, but I couldn’t stall it no matter how badly I handled the clutch.

In 1988 I dated a woman who had a Jetta diesel, and it had definitely improved greatly over the balky early versions, though on a cold morning it still started with all the grace of a Sherman tank.

Today at the shop I drove a 2006 diesel Jetta. Other than a sweet whisper of a big-rig sound, when you goosed the throttle it moved out with ease, power, and grace, easily pulling away from the pack. And that’s almost a decade old. The new ones must be even better, with almost 40 years of engineering in them.

Other manufactures dipped their toes in and out of the diesel waters over the years, but VW never stopped making and improving them. In the early years, diesels were exempt from emission control laws. There simply were not enough of them to justify the complex testing and research necessary to enact regulation.

But by 1984 all the manufacturers recognized this gaping hole in emission law, and rammed more diesels through it than ever before, or ever again. The EPA began drafting regulations, and consequently, most of the manufacturers abandoned the diesel, but Volkswagen kept right on going.

Even better (or worse, as it may turn out), the VW diesel became an alternate “green” car, seeming greener than the Toyota Prius in many ways.

One of the most harmful emissions put out by both gasoline and diesel engines is NOx (oxides of nitrogen). NOx is believed to be responsible for the formation of “smog” in urban areas. Trouble is, in the world of emissions, NOx is the joker in the deck. It forms during peak combustion temperatures (temperatures over 2500 degrees Fahrenheit).

When an engine runs well, it has some pretty high peak combustion temperatures. So in the gasoline engine world, everything you did to improve power, performance, and mileage – and lower emissions of hydrocarbons and carbon monoxide, resulted in increased NOx.

But EPA considered NOx reduction the highest priority, so the car companies essentially de-tuned the engines of their cars in the Seventies, resulting in poor performance and poor fuel economy, the worst of both worlds.

Eventually, with electronic engine controls and three-way catalytic converters, the NOx monster was defeated, and performance and fuel economy and emissions got better than ever in gasoline engines.

But NOx in a diesel is a nightmare. Whereas gasoline engines compress fuel and air at about a 9-to-1 ratio and then ignite in a controlled burn, diesel engines squeeze diesel fuel and air at a 20-to-1 ratio until it gets so hot it just flash explodes.

The combustion gas temperatures in a diesel can reach 5000 degrees Fahrenheit, double that of a gasoline engine. That’s why diesel is more efficient and gets better mileage.

But handling all the NOx produced was evidently more than VW could do without compromising performance. So VW has been submitting doctored cars with “de-tuning” software to government testers.

There is no doubt that, were this de-tuning software in the consumer models, the performance and mileage results would not be nearly as good, and there lies the crux of the problem VW now faces.

There is no fix for this. If there were, Volkswagen would have used it regardless of cost. At some point the EPA is going to have to order VW to fix their cars (put de-tuning software in all of the cars, harming performance and mileage), opening them up to an almost unlimited number of consumer lawsuits, or forcing them to buy the cars back (not economically feasible).

They will most likely pay an enormous fine, de-tune the cars, and be sued by consumers. I’ll be watching how this all shakes out, and I’d love to hear from owners when the action starts. Please contact me with your story at And enjoy driving those cars while you still can!

Sign Up for Our Newsletter

Keep up to date with coupons and promotions


Get exclusive access to them all when you sign up for our newsletter.

Ezytire Toolbox