BMW 320D - the 57MGP wonder on Diesel | Hacker News Reader

BMW 320D - the 57MGP wonder on Diesel

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27 pointsUsNThem23 comments

I do believe that there is a serious negative perception about diesel in the US and combined with low availability of diesel pumps/stations + higher cost/gallon - There seems no incentive to move to diesel.

I am no expert but how does diesel stack up against gasoline on the environmental front ?

This VW-TDI-engine-enthusiast FAQ page suggests diesel's latest engines and emissions systems are better than gasoline when all dimensions are considered -- but US regulations are still gasoline-normative:

http://www.tdiclub.com/TDIFAQ/TDiFAQ-5.html

Diesel is widely accepted in Europe. It used to have problems, because diesel had lower emissions standards often none what-so ever and it took a while for them to catch up, this was due to the fact that gasoline pollutes so much when compared to diesel.

New diesel engines like in the Ford Fiesta are considered to have almost zero carbon emissions, in the UK they don't require road tax IIRC because they're considered equivalent in emissions to an all electric vehicle.

Diesel's main problem is that it releases particulate emissions (unburned carbon), however in most new diesels these are handled by autoregenerating filters (they clog up with soot until saturation point and then quite literally set on fire, burning the soot efficiently and cleanly and leaving a clean filter). However, synthetic diesel (which is produced more directly from biomaterials than oil production and ethanol production, incidentally making synthetic diesel more environmentally friendly than biodiesel and ethanol replacement gasoline) produces 30% less particulates, so not only is it more environmental to produce, but it's more environmental to burn. Biodiesel is better to burn on the carbon front, however the nitrogen oxides they release are far harder to deal with than soot (IE your maintenance would require replacing filters, instead of the autoregenerating filters for standard diesels) and they still produce soot (so you'd need the autoregenerating filters anyway, so why pay for both on a new engine?).

Diesel is a lot cleaner, and can now easily perform sub-zero starts as a lot of new engines are coming with engine-block heaters (even gasoline engines are coming with this option now, both for efficiency and emission reasons, but also because in the far north gasoline fails just as easily as diesel). This is to increase the efficiency of the engine, but it also dramatically extends the lifespan as an engine wears most when cold.

Edit: I forgot to add two reasons why diesels are often liked in Europe. #1 is that they're more reliable, they have no electrical system (no spark plugs), so even when the starter motor fails or you have a flat battery, you'll never need a jump start, you just need a push. They require a rebuild generally after 250,000 miles, while a gasoline will require a rebuild between 100,000 and 150,000 miles.

#2 They now commonly come turbocharged, and now a lot are coming supercharged as well. This enables many diesels to outperform larger gasoline engines in both power and speed, but they also come with a better power-to-weight ratio than gasoline engines, in fact the highest power-to-weight ratio in the world (IIRC) is a V8 diesel.

"New diesel engines like in the Ford Fiesta are considered to have almost zero carbon emissions"

Carbon as in CO2?

> with low availability of diesel pumps/stations

There are fewer stations that have diesel than have gas in many places, but where is diesel availability low enough to matter?

Trucks get diesel somewhere.

Diesels are great engines, but hard to come by in the US. In Europe the majority of cars, from small ones to big limousines have Diesel engines these days.

The most vexing problem, particulate emissions, has been solved with particulate filters, that burn of the collected particulate cake occasionally, by heating it up to 600 C.

In the US Diesel cars are only available from VW and Mercedes. Due to the recent availability of low sulfur Diesel fuel in the US, new models have come onto the market. VW offers the Jetta and Touareg with the latest technology (common rail) Diesel engines. These are direct-injection turbo-charged, and have excellent fuel economy.

However, I've heard that due to fleet emissions standards, VW will only be selling Diesels for a few years. Which is probably true for Mercedes as well.

Personally, I've been driving Diesels forever, and love the efficiency and torque you get from them.

[EDIT] This article gives a good overview of the state of Diesel in the US: http://www.popularmechanics.com/blogs/automotive_news/423558...

Audi A3 will have a 2.0 TDI model for 2010. The Mark VI (2010) Golf will have come with the same engine, which will launch in NA a month from now.

I routinely get 40-45 MPG on the highway in my 2003 VW Jetta TDI with an automatic transmission while driving between 70-80 mph with the air conditioning running at max. I have never had a problem with diesel fuel quality or availability.

My choice of a diesel was not simply to achieve a lower fuel cost per mile. Maintenance costs and reliability are also better due to the lack of certain systems within a diesel engine (i.e. no spark plugs, alternator, etc.).

Why wouldn't a diesel car have an alternator? You need to generate electricity for all the electrical systems (lights, ac, radio, etc). And instead of spark plugs, you have glow plugs with diesels.

It's important to remember that diesel's carbon content (generally what people actually care about these days when they talk about fuel efficiency) is about 15% higher than gasoline's. So the CO2 emissions of your Jetta are more comparable to a 35-39mpg gasoline car. That's still good, but not that much better than a typical compact (say a Civic or Corolla). My '99 Saturn gets about 32-35 under similar highway conditions.

Basically: there's nothing wrong with your car, and it's a fine choice (as long as you keep it tuned! Diesel's particulate emissions can go south really fast if they're not maintained well). But don't be fooled by volume metrics. It's still no Prius.

generally what people actually care about these days when they talk about fuel efficiency

I'm pretty sure people still generally care about cost, not carbon.

Bought a 2009 VW Jetta TDI in April and have yet to have a tank of diesel that will cause my average MPG curve to have a negative slope. Coming from an 1986 Mercedes 300 SDL who would soot at ever pedal stomp, I cannot find a way to make an exhaust soot cloud in the TDI, even under 0-60 race conditions. Diesel prices have been less than mid/premium unleaded in California since I bought the car.

Let's remember that the testing cycles in Europe and the US are not the same, and that the 57 MPG number isn't explained (well, I just skimmed... but a search didn't find much).

Is it a combined or just highway rating?

In general, the EU cycle gives numbers 30% higher (and even more if you forget to convert imperial gallons back to US gallons).

So while diesel has benefits, lets be careful with the numbers.

Does anybody else feel that stuck-in-the-mud-ness increases for every technological generation? Seems the more thing advance, the more people say "right, THIS is how it should be" and never want to move on. Diesel cars are a good example. FFS, the automobile is less than a century old for the normal person. And yet, people have these ridiculous ideas about what is the "normal" fuel to put in them. And are thus resistant to superior technology.

Also, it is MPG, not MGP.

Or L/100km if you want to use a better format. (see http://nudges.wordpress.com/why-we-misunderstand-what-miles-... )

Agreed about the stuck-in-the-mud --- I think we all do it to some extent - but it can get very frustrating.

why aren't we getting euro diesels in the us?

It used to be the case that US diesel was of inferior quality to European diesel, but I’ve no idea if that’s still the case.

Because there's a negative perception hump to get past in the usa. I tried suggesting a diesel, and everyone complains about how dirty it is and other myths.

There are diesels that get even better millage, like the Audi A2 with a mileage on it's diesel model ranging from 80 to 120 mpg. I never understand why car manufacturers don't make aerodynamic body designs for their cars. A honda insight with a diesel engine gets similar mileage.

It used to be difficult - to the point of being impractical - to make a small diesel car run cleanly. IIRC, the technology really only arrived about 5 years ago. Also, large trucks belching plumes of black soot were pretty common until recently, and this is how many people here still think of diesel.

Edit: reference http://en.wikipedia.org/wiki/Diesel_engine#Emissions

I'm no expert but I believe the sulfur content is higher in North American diesel, but that's not too hard to handle, I think that's the old excuse and there are fairly clean ultra low sulfur diesels you can now buy. To pass California emissions, you need to put some sort of aqueous urea tank in to the exhaust system like an AdBlue or BlueTec and those cost a couple thousand dollars (I want to say it's like $3000 on a diesel sedan like a Subaru or the 320D)

I'm not sure why the costs are so high, it may be a patented technology, there isn't anything terribly exotic in it though.

If you can legitimately get in the 40-45mpg range, it's still a pretty good deal. A Lexus RX hybrid still only can get like 30mpg.

At least where I live (NH), diesel is more expensive than gasoline due to higher taxes.

Also, modern refining technology allows a greater percentage of a barrel of oil to be made into gasoline, and the low-sulfur mandate has also added to the cost of production.

Diesel fuel used to be in some sense a waste product and thus historically was cheaper than gasoline. It's only been within last 5 years or so that diesel has been consistently more expensive than gasoline, at least in the US.

We didn't get ultra low sulfur diesel here until a few years ago: http://www.greencarcongress.com/2006/06/ultra_lowsulfur.html

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