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Comment by _nedR | Hacker News Reader

It seems to be game over for diesel cars in general, even if you ignore their eventual replacement with electric cars. They have been getting a lot of bad press lately. Their popularity was due to their higher fuel efficiency; But for diesels, it seems that there is trade-off between fuel efficiency and NOx emissions (http://www.livescience.com/52284-volkswagen-scandal-clean-di...). With many cities and countries trying to curb smog and air pollution, diesels are on the top of the hitlist.

edit: reworded, and changed link

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diesels are popular in europe for one reason that probably somebody from us will not understand. the price of fuel. because the price of fuel is so much bigger fuel efficiency is the biggest concern

A big part of diesel's fuel efficiency advantage is caused by the emissions controls on gasoline powered vehicles.

Vehicles from the early 70s often had similar gas mileage to smaller lighter vehicles from the late 90s-early 2000s but the newer cars had much better emissions.

If the makers of gasoline powered cars had cheated like VW did on their diesels, the diesel advantage would have been nonexistent.

Even if you had no emissions laws diesel would still have a large fuel consumption advantage. Diesel contains more energy per volume (139000 btu/gallon vs 124000 btu/gallon).

In addition the design of a diesel engine does not require a strict stoichiometric air/fuel ration. The result is at less than full throttle the gasoline engine the efficiency of a gasoline engine drops off faster than a diesel engine. In an ideal efficiency engine (no emissions) a gasoline engine at full throttle is more fuel efferent than a diesel engine, but when at less than full throttle - which is where most engine spend all their time) the diesel engine is more efficient. Note I skipped a dozen pages of disclaimers on the above claim: there are many ways in the real world to cheat the above.

> Vehicles from the early 70s often had similar gas mileage to smaller lighter vehicles from the late 90s-early 2000s but the newer cars had much better emissions.

Source? Electronic fuel injection with closed-loop fuel/air control wasn't a mature technology in the 1970s, and open-loop fuel injection (not to mention carburetors) combined with 3- and 4-speed transmissions are inherently less efficient then closed-loop with 4, 5 and 6-speed transmissions.

In Germany it is not just about the efficiency: diesel fuel is taxed lower per liter than gasoline, for exactly the same stupid reasons personal cars are (were?) often cheaper to register in the USA if you find an excuse to call it a truck.

I was offered to register my escape as a truck or a car in Missouri- but registering it as a truck would have costed more. Apparently had something to do with the max weight loading I could theoretically legally have on it.

About the same in France: heating oil was traditionally used to heat houses, but with the development of nuclear electricity it consumption dropped. French government back then helped the refineries by lowering the taxes and pushed the car industry to develop diesel cars. And we have been stuck with these diesel cars since this era.

It's a vicious circle because owner of diesel cars may think twice before voting if a candidate proposes to raise the taxes on diesel, even if year after year we get reports about the number of early deaths because of fine particles…

I've stopped worrying about it completely. I used to have a Nissan Qashqai, with a 1.6dCi engine - my average diesel consumption for 3 years I had that car, was about 7.0L/100km. I now have a Mercedes with a 2.0L turbocharged petrol engine - my average consumption so far is 8.5L/100km of petrol. My fiancee has a VW Polo with a 1.2L petrol engine, and she averages 6.5L/100km of petrol. I literally don't see a point of buying a diesel car, ever again.

Probably fairer to compare your Mercedes to the same model with a diesel engine, and likewise your Nissan.

Wiki says the 1.6dCi is available in 130-180hp whereas the 1.6 petrol has 107-116hp

Fuel consumption will vary due to a lot of different factors, such as aerodynamics, transmission, driving style etc.

he probably means its not that big of a difference for him. and sure, if you dont drive a lot then it does not matter.

when i drove 30k per year i drove a diesel, now im driving 15k per year and drive a gasoline car.

I'm just saying you have to compare apples to apples.

My diesel Peugeot 306 1.9 did about 45mpg no matter how hard I drove it, whereas my friend with the same model with a 2L petrol engine said he was using roughly twice as much fuel as me. The later common rail 2L version was supposedly capable of 55mpg

No, thats just one reason. Disel engines are doing way more kilometres in average before they blow up. Nearly all Taxi/Cabs in Europe are Diesel for that reason.

I really doubt people care about the emission stuff at all...

SRC: http://www.honestjohn.co.uk/forum/post/index.htm?t=16748

i doubt many people buy diesels for they ability to drive beyond 200k miles. taxis are something different

diesels are for taxis suited (beyond that they consume less fuel) because they have torque down low and are not rewed as high as petrol engines, and thus not that abused.

look at large natural aspirated V8s, there are many with close to 1m miles, they pull small power form large displacement but could run forever.

Actually a lot of taxis are Priuses. In some places they give massive discounts to taxi drivers on hybrids, because people were worried about the reliability of the engine and Toyota figured out that seeing hybrid cabs would be more effective than any advertisement.

Not only the price of fuel, but the relative price of the two fuels. In the US, diesel is a fair bit more expensive than regular gasoline, which cuts down or eliminates any cost savings you get from higher efficiency.

It is cheaper than premium gas in most places though, and given the cars diesel engines are offered in, diesel tends to compete with premium, not regular. The obvious exception are 1/2-1 ton trucks, but in those, diesel engines serve a different purpose than the gasoline ones.

Seems to be true in the higher-end diesels, like the BMWs and Audis and Mercedeses, but the gas versions of cars like the Cruze and the Jetta use regular gas. For people who are cost conscious, I imagine that they'd be looking at the lower-end diesels where the gas equivalents use cheap gas.

Not sure about the Jetta, but the diesel Cruze is so much more efficient than the gasoline version that diesel has to be 1.5x the price of gas for the latter to make sense. EPA cycles tend to underestimate the fuel economy of diesel TDIs and overestimate those of gasoline TDIs. They're pretty accurate for non-turbo gasoline DI engines though.

After my diesel car had trouble starting in -15°C temperatures, I will avoid buying a diesel car again. I like the diesel engine for its high torque and the fact that I pay less for fuel, but gasoline is cleaner and I can install a LPG kit if I want cheap, cleaner fuel. A gasoline powered hybrid vehicle negates all the advantages of diesel.

Diesel is really for trucks, ships, agricultural and construction vehicles and some railway engines. It should be taxed more than gasoline because of NOx, particulate and sulphur pollution.

If you regularly drive long distances on highways, diesel >> gasoline-electric hybrid, since the electrical part of the drive train doesn't do much at constant speeds.

> It should be taxed more than gasoline because of NOx, particulate and sulphur pollution.

Diesel car owners already pay that tax through the expense of urea injection, oxidation catalyst, and particular filter systems, and with those systems diesel is every bit as clean as gasoline. Sulfur is a nonissue with ULSD these days, and if you want to reduce sulfur further that's something you deal with at the refinery, not the pump.

> But for diesels, it seems that there is trade-off between fuel efficiency and NOx emissions

Correction: there is a trade-off between fuel efficiency, NOx emissions, particulate emissions, and cost. Urea injection + diesel oxidation catalyst + diesel particulate filters pretty much solves all emissions problems with diesel engines, and that's what GM and Ford diesels do, both in Europe and in the US. It isn't cheap for sure, but the 2014 Chevrolet Cruze diesel is worth every dollar in premium over the gasoline version.

The modern highly-compressed Gasoline Direct Injection engines are a potent source of soot, though. Eg http://www.sciencedirect.com/science/article/pii/S0301679X15...

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