CVille Dem's picture

    Is it True that we are at the mercy of the Rockefellers? Donal?

    By CVille Dem on Sun, 03/31/2013 - 8:37pm |

    http://offtheedgehumorpics.blogspot.com/2013/03/vw-passat-785-mpg-imperi...

     

    Sorry, guys.  This is lame, but I am not myself

    Comments

     

    As the speaker alludes, part of the diesel efficiency discrepancy has to do with US-mandated devices that reduce some, but hardly all, of the harmful diesel exhaust. But it may also have to do with the quality of the fuel in use.
     
    There are no spark plugs in diesel engines, and diesel fuel must be able to ignite under compression. Instead of octane, diesel 'oomph' is measured in comparison to a liquid hydrocarbon called cetane, which is given an arbitrary compression ignition value of 100. Within limits, a higher cetane number (CN) means quicker ignition, more complete combustion, and should increase fuel economy in an engine timed for higher numbers. 
     
    In the EU, minimum CN is now 51 and premium CN is 60. Many articles claim a CN of 55 is normal in the EU.
     
    I've read claims that in US regular #2 diesel CN is only 42-45 and that premium is just regular with additives. I've read other claims that US standard CN is 48 and US premium CN is 55. And still others claim that regular #2 CN is only 40-45 and premium CN is 45-50. 
     
    So it may be that European drivers get fuel with CN values about ten points higher. If that's the case, the engines sold here and there should be different.

    by Donal on Sun, 03/31/2013 - 10:39pm

    #2 diesel that is used in heavy equipment is 42-45 CN in the US made from domestic crude. It takes light sweet crude to move the numbers up. That is why Europe was willing to step in and handle Libya. The wells there produce high quality light sweet crude that European diesel is made from. They maybe making a little bit better grade diesel now that is sold at US gas stations for cars. Red diesel was considered better for big trucks when I was driving because of the additives that made it red.

    by trkingmomoe on Mon, 04/01/2013 - 2:17am

    That explains a lot. Saudis have been claiming for some time that they have plenty of crude, but much of that is heavy and sour, which fewer refineries are setup to handle.

    FWIW, biodiesel is supposed to have higher CN values.


    by Donal on Mon, 04/01/2013 - 8:17am

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