re: diesel lube oil

["BILL MITCHELL" <mitch@xxxxxxxxxxxxxxx>]

This talk of using diesel engine oil to clean a gasoline engine out is bunk.
I sell oil(mostly Exxon but other brands as well,) and have been to numerous
schools put on by Exxon lube engineers.  If you will check the bottle most
diesel engine oils are rated both "C" and "S".  This letter is followed by
another, such as "SF"  or "SG"  or "CDII" or some such.  The first letter
tells you whether the oil is designed for a gasoline engine(S for spark) or
a diesel engine(C for compression).  The following letters and/or numbers
are simply the test requirements that the oil has passed according to the
Society of Automotive Engineers(SAE).  As time goes on, the tests get more
and more rigourous, just as the engines get more and more stressful.

When I bought my '95 540i/6  I checked with the dealer service department as
to the best Exxon oil to run, and was told that Exxon XD-3 15W-40 was what
they would recommend.  This is primarily a diesel oil, but also meets
gasoline engine specs.  In fact, this is the oil that I run in all my diesel
trucks(2 Freightliners, 1 Peterbilt, 1 Kenworth, 1 White/Volvo and 1 Chevy).
I ran it for a year until I switched to synthetic oil.

Neither gasoline or diesel oils will "clean" an engine, other than the
normal cleaning that a high quality engine oil will perform.  Cleaning is
one of the qualities of all oils, along with lubrication, heat dissipation,
sealing and rust prevention.  The modern oil carries contaminants to the
filter where they are trapped and held 'til it is changed.

The only oils sold that do not have detergents in them are rated SAE  SB,
and they basically are straight mineral oils, with some mild rust and
oxidation inhibitors added.  Our hydraulic oils qualify as an SB oil, and
years ago when there was a market for such, Exxon sold one of their
hydraulic oils in quart cans as an SB oil.

This is probably more than most wanted to know about oils, so forgive me,
but there are lots of myths around.  My philosophy is to buy a good quality
oil that meets your owners manual recommendations, and change it(and the
filter) regularly, around every 3-4,000 miles.  Additives are a waste of
money.

Bill Mitchell

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