New Study Shows Gas Engines Even Dirtier, EVs Now Even Cleaner

German Automakers

JUL 6 2017 BY EVANNEX 35

Tailpipe emissions from internal combustion engine gasmobiles are a major source of greenhouse gas emissions and pollutants harmful to human health. EVs are the solution. (Image: Living on Earth via Pittou2, Flickr CC BY-NC 2.0)


Conventional wisdom has it that diesel engines are dirtier than gas engines because they emit more particulate matter – tiny bits of soot that can cause serious damage to human lungs. However, a new study led by the Swiss research institute Empa (via Gas2) has found that some gas engines spew forth much more particulates than diesels.

The researchers studied the emissions of 7 gas vehicles equipped with direct fuel-injection systems, and found that they emit from 10 to 100 times more particulates than modern diesel engines – more, in fact, than older diesel engines without particulate filters.

“Once inhaled, these particles remain in the body forever,” explains project leader Norbert Heeb. Evidence shows that they can penetrate the membrane of the air sacs in the lungs and get into the bloodstream. And it gets worse: “Liquid or solid chemical toxins from the combustion process… accumulate on the surface of the particles, which can then smuggle these substances into the bloodstream – like a Trojan horse.”

Those nasty combustion products include benzo(a)pyrene, a known carcinogenic substance that’s found in all kinds of smoke and soot (including cigarette smoke).

The World Health Organization (WHO) considers even a tiny dose of benzo(a)pyrene harmful. Levels in vehicle exhaust were found to be as much as 1,700 times above the safe limit established by the EU.

*This article comes to us courtesy of Evannex (which also makes aftermarket Tesla accessories). Authored by Charles Morris.

An alarming amount of particulate emissions are coming from gasoline engines (Image: Gas2 via Bosch)

Not all gasoline engines form particulates in the exhaust. The culprit appears to be a modern innovation: direct fuel injection. In older electronic fuel injection systems, fuel is added to the combustion chamber at the end of the exhaust stroke. In direct-injection engines, the fuel is added after the end of the intake stroke. This gives the fuel less time to evaporate, says Heeb, resulting in more unburned hydrocarbons and thus more soot.

Automakers began adopting direct injection because it allows more precise control of the fuel delivery process, leading to better fuel economy and lower carbon dioxide emissions. The new study seems to be one of the first to test direct-injection engines for anything other than CO2.

Heeb and his team urge automakers to begin equipping their cars with particulate filters. “New exhaust emission technologies launched on the market typically need about 13 years to become fully effective,” writes Heeb. “Only after that period of time will 9 out of 10 cars in the vehicle fleet be replaced. So, the faster particle filters are mandatory in gasoline cars, the better it will be for everyone’s health.”

Above: Cities like Beijing are pushing for electric vehicles in order to reduce emissions (Youtube: CGTN)

Particulate matter is only part of the toxic mixture that hovers around cars and roads. We all regularly breathe in nitrogen oxides, volatile organic compounds, ozone, carbon monoxide, benzene and other nasties. In a recent article in the Guardian, Professor Sir David King, chief scientific adviser for the English government, warns that levels of air pollution are often far higher inside cars than outside them, as indicated by several studies. A study in Copenhagen found that a driver breathed in more pollution than a cyclist on the same road. Outside, the emissions are diluted by the surrounding air, but inside a car, the dirty air circulates and builds up.

As Sir King notes, the UK is considering a ban on smoking in cars, in order to protect children, but the wee bairns may actually be at greater risk from air pollution. “You may be driving a cleaner vehicle but your children are sitting in a box collecting toxic gases from all the vehicles around you.”

One automaker is fitting its vehicles with filters that clean the air that drivers and passengers breathe. The heavy-duty HEPA filter was first available in Tesla’s Model X (and later in its Model S) and it’s about 10 times larger than an ordinary car filter. Tesla claims it is “100 times more effective than premium automotive filters” and that it removes “at least 99.97% of fine particulate matter and gaseous pollutants, as well as bacteria, viruses, pollen and mold spores.” In 2016, the company tested the filter, and found that not only did it scrub the cabin air clean, but even began to vacuum up pollutants from the outside air.


Tesla putting its HEPA filter and “Bioweapon Defense Mode” to the test (Image: Tesla)

Even as legacy vehicles get dirtier, electric vehicles (EVs) are clean and getting cleaner. Numerous studies have found that, thanks to their far greater efficiency, EVs in general produce less emissions than gas vehicles, even if powered by coal-generated electricity. However, the mix of power sources varies widely among different parts of the world, so EVs end up being greener in some regions than in others.

A new report from the Union of Concerned Scientists, which updates and expands upon an earlier study from 2015, found that driving electric is now cleaner than driving a typical gas-burner everywhere in the US. Furthermore, the electric advantage is growing as more regions are cutting their use of coal and increasing investment in renewable energy sources. The new analysis is based on updated data from the EPA, which shows reduced greenhouse gas emissions from power generation in most of the country over the past five years.

According to the new study, in 70 percent of the US, driving electric produces fewer emissions than driving a gasoline car that gets 50 mpg (a figure met by only the Toyota Prius and the new Hyundai Ioniq). On average, today’s EVs are as clean as a hypothetical gas vehicle that gets 73 mpg.


For over 70% of Americans, driving an electric vehicle results in fewer emissions than even a 50 MPG gasoline vehicle (Source: Union of Concerned Scientists)

“Driving electric is one of the best choices a consumer can make to reduce emissions in their own lives,” said David Reichmuth, Senior Vehicles Engineer at UCS. “As the electric vehicle market has emerged over the last five years, electric vehicles are better than a 50 mpg gasoline car for 70 percent of Americans, up from 50 percent. It’s been remarkable to see the improvements.”

Of course, it’s not enough to consider only tailpipe emissions. What about the pollution produced in manufacturing a vehicle? Several studies have examined the cradle-to-grave life cycle of an EV, including a recent offering from Like Tesla. Producing an electric vehicle, especially one with a large battery pack like Model S or Model X, requires a lot of energy – that’s one of the reasons Tesla decided to bring the battery manufacturing process in-house at its Gigafactory. According to Like Tesla, manufacturing an electric car actually produces more greenhouse gas emissions on the front end than manufacturing a comparable legacy car.

Above: Looking at how electric vehicles are better from the ‘cradle to the grave’ than their gasoline counterparts; Editor’s Note: This was filmed before the latest Union of Concerned Scientists report which means that EVs numbers have actually improved even more since this video was published (Youtube: Like Tesla)

However, once the vehicle leaves the factory, the equation is reversed. An internal combustion vehicle will produce more emissions than its electric cousin with every mile driven. Like Tesla found that, over its lifetime, a typical internal combustion vehicle will produce 160,000 pounds of greenhouse gas emissions, compared to 82,000 pounds for a Tesla Model S (smaller and more efficient EVs, such as a Nissan LEAF, will produce even less).

Another oft-cited environmental hazard is rare earth metals, which are used in all kinds of modern products, from cars to consumer electronics. Tesla has long avoided them, as it stated in 2012: “Tesla does not use rare earth metals in our batteries or our motors. Typically rare earth metals apply to DC motors, which use magnets. One of the reasons we use an AC induction motor is it does not require magnets, which often contain rare earth metals.” Tesla also recycles the vast majority of metals used in its battery packs.

Some EVs (and legacy vehicles) do use rare earth elements, but the clear trend in the industry is to phase out their use. Automakers and motor suppliers are developing new technology to recycle rare earths, minimize their use, or stop using them entirely.

*Editor’s Note: EVANNEX, which also sells aftermarket gear for Teslas, has kindly allowed us to share some of its content with our readers. Our thanks go out to EVANNEX, Check out the site here.

Categories: General

Tags: ,

Leave a Reply

35 Comments on "New Study Shows Gas Engines Even Dirtier, EVs Now Even Cleaner"

newest oldest most voted

Currently gasoline cars with that kind of technology are allowed to emmit 10 times as much particles as diesel cars in Europe.

But this will change (this september) i think.

Gasoline cars currently arn’t required to have an PM filter while diesel do. This is the reason for it. With an PM filter they are better again.

Actually that isn’t even remotely true, at least according to any tables that I’ve seen, like this one:

Since Euro 6 came into effect in 2014 for all new models and in 2015 for all new cars, Diesels and DI gasoline cars have been subject to exactly the same standards.

The fact that they may only meet those standards under very specific testing conditions is another matter though.

On second thought, I take that back. The particulate standards have actually been the same since Euro 5 came out in 2009!

It is not that simple as single number. EU tends to create norms that look nice on paper, but then corruptio.., sorry lobbying takes its way and automaker countries add bunch of loopholes that reverses everything in practice. There are different PM sizes and different operating conditions, and regulations are not exactly the same for diesel and petrol engines.

Corning (the catalyic convertor people) has an entire product line for just this problem, it’s loosely based on the same technology as their diesel filters.

And it’s doing expansions to support demand in both China and Europe.. So yes, GDI is “dirtier” but more efficient, and it can be cleaned up with emissions systems (just like a ICE and diesel – assuming you willing to add such a system to a diesel – which apparently not all Germany companies were willing to do, or honestly believed they could control with engine tuning software)


So yea, while EV’s are certainly cleaner, GDI engines are a good thing, assuming emission laws require GPFs

Toyota has a simple solution to the problem – don’t use GDI and still beat everything in fuel economy.

But at the end of the day, the only thing that can lower the polution is regulation and strict testing. The ones that think that EVs will save the day in next couple of years are living in a fairytale.

Toyota may be more conservative pushing untested designs to mass production, but eventually they do, and direct injection is no exception:
Camry 2018 uses it, that is how it achieved record 52 mpg rating.
They had direct injection in other cars & trucks for couple of decades:

Excellent article. People underestimate how harmful ICE cars are.

Does the GDI part of this article applies in the US or CA? Aren’t there different engine standards here? Also, I thought that I had seen a decent study from a USC researcher that found in-car pollution could be kept low with your A/C kept on recirculate (and windows up).

As UCS updates its maps, and talks about 50mpgs, I was just looking at the U. Mich tracking data today showing US fleet economy basically stalling near 25mpgs.

This is pretty much everything under 6,500lbs:

This article is incorrect in that direct injection is not for more precise metering of fuel and leads to less evaporation.

Direct injection is used at high pressure to create better fuel atomization. This increases the surface area of the fuel particles to increase flame propagation speeds allowing for combustion to occur with ignition timing closer to top dead centre which reduces wasted energy. Direct injection actually improves fuel evaporation causing a cooling effect which also allows for higher compression ratio’s which also improves a vehicles thermodynamic efficiency.

What is the cause of increased soot emissions in in cylinder direct injection compared to port injected gasoline engines?

Not sure if I rember correctly from previous articles but it could be from them using the GDI injectors to spray unburnt fuel into the cylinders to cool them…

I’m pretty sure they messed up on that. It makes zero sense for GDI to suffer from soot! I only know a runny but from Wikipedia about this, but here’s what I got: Without GDI, the way to run the engine at less than full power is to reduce the throttle opening. This reduces the efficiency of the engine because it takes more energy to push air past the partially closed throttle than a wide open one. With GDI the fuel is injected directly into the combustion chamber, not the intake manifold, and this makes it possible to run the engine with the throttle fully open at low power levels, such as when going at a steady speed on a flat road, by injecting a much smaller amount of fuel than would be mixed in if pulled into the combustion chamber by the airflow. Air to fuel mix ratio can be as high as 65:1 by mass, much more than the 14.7 or so theoretically required for complete combustion. The large amount of air allows higher compression ratios, which leads to higher power, lower consumption – and much more NOx. Apparently this has always been known, so it appears the… Read more »

I always wondered how they handle soot problem with GDI, it looks like they never did. High efficiency with ICE has penalties; too lean means too much NOx, direct inject means soot.

Wouldn’t it be interesting if they tested the prius to see just how clean that car really is? …or maybe we don’t want to know…

Prius being Atkinson cycle, I don’t think emissions will be worse than typical gasser. But the problem with Atkinson is much lower power. Prius at 1.8L, 98HP is about the same as SparkGas 1.4L. 1.8L Otto in Corolla makes about 135 HP.

I wouldn’t care if EVs were twice as dirty overall. EVs are getting better, both by manufacturing and by power grid. ICE engines are not getting better.

There is a pollution factor inherent in the use of ICEs that these studies never address.

That is the amount of crap introduced into the environment from the repair and rebuilding of engines.

Incredible amounts of pollutants are created from the simple act of cleaning burnt and blown up engine parts. I know because I was a mechanic for 20 years before getting into EVs.

Even if you grind up what’s left of a vehicle at end-of-life, all that stuff still finds it’s way into the ecosystem.

I call BS. You claim to know this because you were a mechanic, but a subjectively impressive-to-you amount of emissions need not actually amount to anything significant compared to the huge total.

If you do have the numbers I will be very happily and easily corrected. Just post them along with link to a proper source. If you do not have the numbers, please explain how you know that this is significant (other than to the health of the mechanic, which is very important but a completely separate issue).

Sadly, even though gas/diesel emissions standards are improving, people who don’t maintain (or willfully bypass) their emissions systems are causing massive pollution.

These “Gross polluters” emit HALF of all total pollution!! When you see a truck “rolling coal”, they are polluting more in a few minutes of rolling coal than an EV does in a year.

I think you’re seriously understating the problem, Nix. Even when I took an Environmental Science course in college in the mid-1970s, my teacher knew enough to explain that 10% of the vehicles on the road emit 90% of the pollution… just like the one pictured above. He wasn’t just guessing at the ratio; some States require emissions tests before renewing license plates.

Has the situation improved since the 1970s? I doubt it has improved much, if any. We still see on every road that a small percentage of vehicles — including some diesel semi trucks — are visibly spewing out soot and smog from their exhaust pipes. If we could identify those vehicles and revoke their tags until they cleaned up their act, it would go a long way toward reducing the air pollution we’re forced to breathe.

Drive in DFW sometime.

There are loads of older trucks in the 3/4 to 1-ton size that are hauling trailers for various work. They pollute more than hundreds of other vehicles. If not thousands. Each. They visually blow smoke.

When I’m behind one of them I go to recirc on the HVAC and try to get around them. I can feel my paint wearing away from the acid bath.

“…the faster particle filters are mandatory in gasoline cars, the better it will be for everyone’s health.”

Better yet: The faster gasmobiles are replaced with long-range plug-in EVs, the better it will be for everyone’s health.

I’ve always thought it was a mistake to focus on CO2 emissions. The actual pollution, especially the carcinogens and the toxic gasses, are a far greater threat to public health than the piffling one degree or less of global warming that comes from transportation emissions.

Exactly why EU is on a diesel economy. CO2 was the only criteria.

I wouldn’t dismiss several degrees of warming. The system can be upset by less change than that. If more polar ice melts it could reverse flow in the ocean and cause UK to be in full-on winter all year long. Happened before.

I believe it is the Greenland ice sheet, not the polar cap, that is considered a threat to the Gulf stream. But I completely agree that what seems a small change in global temperature does not mean the consequences are small. There’s every reason to believe they will be very unevenly felt in different places, but very severe in many.

And if things go the way I think, new dangers will emerge soon. In the absence of the kind of radical change that’s required to halt and reverse the growth in atmospheric greenhouse gases, I think pressure will start to build to attempt active mitigation by deliberately altering the atmosphere. That would be some experiment, but because there will be billions to be made in it, surely there will be strong lobbying and manipulation of media and voters. Maybe it will be a huge success, but more likely our first attempts at Terraforming will be disastrous…

It’s an interesting time to be alive if nothing else.

So now you think yourself an expert on public health and global warming and how to weigh the two against one another, in addition to most other things.

The mark of an educated man is that he has grasped the scale of his own ignorance. By that measure I’m led to guess you were a self-taught programmer…

Let’s agree that it is not a good idea to consider ONLY GHG emissions to the exclusion of everything else. But to “focus on NOx” or particulates while ignoring GHG would be to make the same class of mistake all over again.

Luckily in this case there’s no need to trade off one against the other since BEVs are better in both respects. They do cause more particulates from road wear due to greater mass, but the total is still a reduction compared to setting fire to extremely old plant matter.

“So now you think yourself an expert on public health and global warming…” I find it rather amusing how I occasionally get accused of calling myself “an expert” by internet post-ers whose misinformation I have taken the time to debunk and correct. This despite the fact that I have never, ever called myself an “expert” on anything related to any subject discussed on this forum, and never will. Terawatt said: “The mark of an educated man is that he has grasped the scale of his own ignorance.” I think that’s a sound principle, and I also agree with the principle that no man is qualified to judge his own expertise on a subject. I am gratified that certain other people (not members of this forum) have called me an expert on one very narrow subject (a literary topic irrelevant to the discussion here), and I believe I do understand the depth of knowledge that a real expert has in a given field… which I certainly do not in regards to electric cars, electrical engineering, the automobile industry, business financing, environmental science, or anything else discussed on InsideEVs. But one often doesn’t need to be an expert on a subject to… Read more »

“This is frankly ridiculous. The temperature swings between ice ages and interglacial eras are about 10 degrees, no disaster has resulted from that…”

Look up ‘snowball Earth’- which has happened more than once.

Citing is sufficient to blow any credibility you might have had.

Known to promote known falsehoods way after conclusive evidence.

Motivated reasoning abounds

They state that an electric car is now better than a 50 MPG car in 70% of the US. But what’s not so clearly said is that’s just with respect to emissions from driving it, right now. Over the life of the car, the electricity mix will become much greener, especially in those 30% of the US where the electric car doesn’t immediately beat a Prius. In other words it’s almost certainly better, for GHG emissions, to get an electric car than a Prius in 100% of the US.

“although gasoline direct injection engines dramatically reduce CO2 emissions, they release about 1,000 times more particles classified by the World Health Organization as harmful than traditional petrol engines and 10 times more than new diesel engines.”

How could you write this article without including “ULEV” and “SULEV” ratings?