

BMW 320D - the 57MGP wonder on Diesel - UsNThem
http://www.wired.com/autopia/2009/08/high-end-low-emissions-bmw-unveils-a-57-mpg-diesel-3-series/

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UsNThem
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 ?

~~~
gojomo
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>

~~~
electromagnetic
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.

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

Carbon as in CO2?

------
car
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...](http://www.popularmechanics.com/blogs/automotive_news/4235586.html)

~~~
papersmith
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.

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tumba
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.).

~~~
ajross
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.

~~~
mmt
_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.

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MikeCapone
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.

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porkcharsui
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.

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

~~~
elai
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.

~~~
sp332
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>

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sho
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.

~~~
whatusername
Or L/100km if you want to use a better format. (see
[http://nudges.wordpress.com/why-we-misunderstand-what-
miles-...](http://nudges.wordpress.com/why-we-misunderstand-what-miles-per-
gallon-ratings-are-telling-us/) )

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

