T&T: Cummins engines and low sulphur diesel

[B.]

I sent a question recently to Cummins engine regarding the new diesel on the
market. This is the official answer, some listees might be interested :

Bryan

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Summary: New diesel


There are many rumors circulating about the effects of sulfur being in
diesel fuel or sulfur being taken out of diesel fuel.  Diesel fuel without
sulfur is just as good, in all respects except one, when compared with
today's fuels with sulfur.

Diesel fuel, in the United States, must meet a lubricity standard.  The
producers adjust the lubricity before they distribute the fuel.  No further
additives are needed to ensure proper fuel system lubrication.

The only negative effect of taking sulfur out of fuel is that the fuel
becomes more expensive, somewhat negating the inherent cost advantage of
running diesel engines when compared to other fuels.  As we are certain you
know, sulfur doesn't jump out of the fuel on command.  It has to be removed
using specialized equipment and chemical processes that add to the expense
of producing the fuel.

We have seen a very few instances where the reduced aromatic content of the
fuel has resulted in slight leaks from fuel systems.  This is not expected
to be an issue with many engines.

Basically the change to new fuel should be pretty easy for folks with the
engines built prior to 2007 and for customers with the engines built in 2007
it will be necessary, for the short time it takes fuel stations to consume
the remainder of the old fuel (maybe a month or two), to be certain they are
not fueling with the older fuel.

There is an effect on diesel engines from the use of low or no sulfur fuel
which we expect to be positive.  The blowby gasses that normally pass
through the engine crankcase will contain less or none of the chemically
reactive sulfur and its compounds.  This will tend to keep the engine oil
cleaner during operation and allow important engine components like
bushings, bearings and piston rings to live longer.

Diesel fuels containing sulfur or no sulfur each have the same specific
heat, about 20,000 BTUs per pound.  For that reason they give the same
amounts of work for the same amount of fuel.  That means the fuel economy
per gallon will not be affected.

Over the years we have seen fuel economy decrease, somewhat, as diesel
engine designs have been modified to meet the lower NOX limits imposed by
government.  This has been totally unrelated to sulfur in the fuel.

With lower sulfur fuels it is possible that some exhaust after treatment
devices (catalytic converters) may be used to better effect, making it
possible to further decrease harmful exhaust emissions.

If you use diesel fuel that does not meet the new federal low sulfur
requirements that are going into effect for 2007, in a 2007 vehicle that
requires the new fuel, it will produce particulate matter that will cause
rapid plugging of the exhaust particulate trap.  We don't anticipate
producing engines for such vehicles until 2007.



Customer Assistance Center
Cummins, Inc.
Columbus, Indiana, USA