Soot, Diesel, And Buying A New Car

By Gina Carroll

In the clean air arena, diesel is a dirty word… and I know from personal experience all of the reasons why diesel fuel has a bad reputation. So when my husband suggested that I consider the diesel-fueled option in my current search for a new car, I cringed because I can conjure up memories of the diesel car we owned in the mid-1980s. Not only was the car sluggish and the engine embarrassingly noisy (Stop the knocking! Stop the knocking!), but it spewed out a black, smelly cloud of  pollution with every push on the accelerator. Our younger, more economically limited, less environmentally savvy selves were ecstatic about the car. Even though diesel fuel dispensing stations were more difficult to find in those days, the prices were considerably less than regular fuel. We didn’t have to hunt stations down nearly as often as we did for our regularly fueled car because our diesel car got around 50 miles to the gallon. Obviously, we loved the economics.

When I think about how our daily commute contributed to the already atrocious Los Angeles smog, I am mortified. Because of our past sins, we cannot consider buying a diesel-fueled car again. Or can we?

In the face of what we know now about diesel emissions, and the image of our old diesel engine belching out nasty black smoke and emitting carbon monoxide, sulfur dioxide, nitrogen oxide, and soot, why would we even be talking at all about purchasing a diesel-fueled car? And given all of the regulations the EPA has issued for various forms of air pollution, including the most recent regulations for soot pollution, diesel vehicles have historically been at the top of the offender’s list. So how has diesel made the big comeback that it has? And more pointed to my new car search, is diesel car ownership a selfish economic trade-off?

Apparently not. Drastic changes in diesel fuel and the technology of car diesel engines have made diesel a contender, even for those of us who seek to make environmentally conscious transportation choices. The question remains: Are those changes good enough?

According to the manufacturer of our old diesel car, their new diesel engines reduce total output of harmful emissions by 80 to 90 percent. This level of clean is achieved (according to the car maker) by a system that filters exhaust from the engine through a device that lowers carbon monoxide and hydrocarbon levels. Then it runs through an apparatus that removes soot and other particulates. Finally, the remaining exhaust gas is sprayed with a urea-based substance that helps convert harmful nitrogen oxides into harmless nitrogen gas and water vapor. The car maker says that the process provides clean emissions, and it even eliminates the awful smell.

Diesel fuel efficiency also helps to reduce emissions. Electronic and engine advances contribute to maximizing fuel economy in engines that have always been relatively fuel-frugal. Part of their efficiency, according to Popular Mechanics, comes from their high compression ratios. The importance of compression ratios is this:

“…The higher the compression ratio, the more mechanical energy an engine can squeeze from its fuel/air mixture. So each time the mixture in a diesel engine’s cylinder ignites, the car gets a slightly bigger push than it would in a gasoline engine. That means it takes less fuel to move the car down the road.”

This compression ratio is also why diesel engines last so much longer than gas-fueled engines–this has something to do with lubricants and friction.

In response to EPA regulations that went into effect in 2006, oil refineries had to produce “ultra-low-sulfur diesel,” a 98.5 percent cleaner product than what was allowed previously. More recently, in an EPA hearing about how clean diesel emission is reducing soot emission in the U.S., Tom Fulks, of the Diesel Technology Forum, said that over the last ten years,

“…the diesel industry has invested billions of dollars in development of cleaner diesel fuels, advanced engines, and emissions control technology… according to the most recent public EPA emissions inventory data, diesel engines of all kinds make up less than six percent of the national particulate matter [soot] emissions inventory.

The combination of the monumental reduction in emissions and fuel efficiency makes diesel engine cars serious contenders. And I have to say–in the alternative fuel, green transportation world, it’s refreshing to see that the diesel industry has taken big and bold steps to answer the call for cleaner burning, longer running options. As diesel gets cleaner, it gets more expensive. But then, according to the EPA, cleaner, greener cars help health costs go down. That’s a trade-off I can live with.

Will I opt for a diesel-fueled car? I don’t know. I recently visited my hometown, Los Angeles, and as I drove in from the airport in the wee hours of the morning, I found myself sitting in traffic on the 405 freeway. Increasingly, in Houston (where I live), the traffic is looking very LA-like. So between the 24/7 traffic, and all of this talk about soot, my next vehicle may very well be a bike!




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.1 years ago

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.2 years ago

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Past Member
Past Member 2 years ago

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Past Member 2 years ago

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Warren Webber
Warren Webber3 years ago

Live long and prosper

John B.
John B5 years ago

Thanks Dominique. for providing Ms. Carroll's very informative article.

John S.
Past Member 5 years ago

Look at diesels in Europe, they rule.

Dave C.
David C5 years ago


Lauren Weinstock
Lauren Weinstock5 years ago

And my son's t-shirt says his other car is a bumper car. We really do need to re-think some of this stuff. Sadly, I doubt it will happen in time.

Geraldine T.
Geraldine T5 years ago

It's hard to make a choice between renewable energy & fossil fuels for our cars, but if the people who do the research on how we can run our cars greener, it could not only save the world from more pollution but would make it unnecessary to destroy the last habitat of animals like the Sumatran orangutan who are going to be extinct in the wild by Christmas, because the last of their forest was burnt down last week to grow palm oil to sell as fuel. How long will it take before we have totally destroyed the rest of the environment, because when it's gone so are we.
It might be better to go for diesel but it's still fossil fuel, & growing fuel is just as damaging to the environment.