Comment by titzer

8 years ago

> It's problematic and I'd love to skip it on my next purchase.

I'd like you to go ahead and not pump a crapton of pollution into the air, thanks. Sorry for being so direct, and I would generally prefer to be more civil, but your comment strikes me as incredibly tone deaf and frankly, destructive. You are one inch away from advocating peeing in the swimming pool because it's cheaper than building toilets.

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titzer

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joecool1029  8 years ago

Since you probably haven’t owned a modern diesel vehicle I’ll tell you why owners don’t like the equipment on small vehicles. (Cars and light trucks)

It mostly comes down to the diesel particulate filter (DPF) that reduces visible soot. This is not really a problem outside some major cities.

Why don’t we like the DPF systems? Consider something like a VW Golf or Jetta TDI. With these systems you’re adding hundreds of pounds of extra dead weight, a regen cycle is required which wastes fuel by blowing it into the filter to regenerate. Combined, this wastes around 10-15%. The cherry on top is you cannot run blends of biodiesel higher than 15% or it ruins the DPF since it doesn’t volatilize like diesel does. Biodiesel is renewable and already comes with reduced emissions without extra controls.

I do give a bit of a shit about the environment and if given the option I would not have a DPF on a light diesel. I have a hard time seeing how decreased fuel mileage and a restriction on running renewables equals care for the environment.

Keep in mind, we removed sulfur from our on-road fuel in the US back in 2007 (way behind europe). This was a big help in allowing new catalyst controls to work as well as reduce conventional diesel pollution.

But yeah, this is not stuff most people consider or know about until they own a noxwagen after previously owning one of the pre-2007 tdi’s, read the bosch whitepapers on the controls, and have a dpf fail just outside federal emissions warranty (VW’s motto: If you can program it to cheat, you can program it to fail!)

EDIT: Forgot to mention the cost of just the DPF is usually $4-6k. It’s a huge failure component and I can’t recommend anyone purchase a lightt vehicle with one for city use as it won’t be able to properly regenerate and will fail early. Since the cost is that high the car/truck may be prematurely scrapped.

  • noelwelsh  8 years ago

    How available is biodiesel in the US? I"ve never seen it here in the UK, so it's not a consideration for me.

    The DPF should be self cleaning if you do an occasional high-speed trip (such as on a highway), so it shouldn't be wasting fuel unless you're doing exclusively city driving (in which case I agree; petrol or electric is better in this situation).

    Our 2016 Golf Bluemotion gets at least 50mpg in normal driving, usually over 60mpg, and occasionally we crack 70mpg.

    • joecool1029  8 years ago

      >How available is biodiesel in the US?

      Wholesale its pretty much everywhere. Retail it depends on the state. Most states have a small % (usually 2-5%) blended into standard diesel to replace the lubricity lost from removing sulfur, but to get B20 or higher you’d have to google.

      >The DPF should be self cleaning

      Key words, ‘should be’. Do a quick search of dpf problems. They either plug from not completing (though you get dpf light telling you to go race it for a half hour or so to clear) or having some other issue. This causes obstruction and reduces economy more. That or they crack like mine did and plug the egr with soot. Regen takes some time to run, if your commute is 5mi it will not complete.

      >Our 2016 Golf Bluemotion gets at least 50mpg in normal driving, usually over 60mpg, and occasionally we crack 70mpg.

      (Casual reminder UK mpg different than US mpg, I will convert my experience to UK mpg)

      Consistent with my 98 jetta tdi’s mileage. Unfortunately my 2012 golf tdi usually only topped out around 60mpg, I only broke 70mpg in a few extrodinary circumstances. The newer ones have urea injection systems and are a bit lighter.

      Also from what I remember UK diesel is usually higher cetane and generally higher quality (also comparing any US/EU spec vehicles, US almost always detuned for emissions and running on poor fuel)