Re: how much to change the oil

[Jim Ochi <jochi@xxxxxxxxxxxx>]

ChrisBourk@domain.elided wrote:
> I wrote:
> >5.  Some people follow the Service indicator lights for oil changes
> >(usually this means that they have an oil change every 7500-9000 miles).
> >Others change every 3000-3500 and ignore the lights.  Big debate about
> >what's better, no definitive answer.
> >
> >Jim Ochi
> >jochi@domain.elided
>
>I appreciate your desire to invote lurkers to respond but please only post
>good information.

Please re-read this and tell me what part is not good information.  What I
wrote is 100% true - some people follow the fancy electronics and
programming designed and implemented by BMW, and change their oil according
to the SI lights.  Some people ignore all the fancy engineering and change
their oil more often.  Now, I haven't been on the digest that long, only a
bit more than 2 years, but in that time I can't recall anyone posting a
definitive, scientific answer to the oil change issue.  I've seen lots of
opinions. I've seen lots of anecdotes of how people's engines have lasted
300K miles with frequent oil changes but I've also seen lots of anecdotes
of how people's engines have lasted 300K miles following the SI lights.
I've also seen a few people post the results of engine oil analysis, but
what I haven't seen is anyone doing any analysis of buildup of oil
contaminants over time/mileage, and I don't believe anyone has posted
anything correlating levels and types of contaminants with amounts of
engine wear.  

In fact, the only study that I've seen is the Mobil study where they put
one million miles on a 1990 325is, using the factory service intervals and
Mobil 1, tore the engine down, and found everything except two rod bearings
and the #2 piston rings within factory spec. (See the March 1997 Roundel).
The results of this test seem to indicate that following the manufacturer's
service intervals is more than adequate for the number of miles that we're
likely to put on the car during it's lifetime.

>To my knowlege there is really no debate as to how often to change oil - it's
>simple,  the more you change the oil,  the less wear from abrasives and
>contaminants. This is not a subjective/opinion/x/y axis answer,  the more you
>change the oil the longer the engine will last - PERIOD.  This is with all
>other condions equal.  There are no conditions where changing the oil less
>frequently will allow an engine to last longer.

Please give me a pointer to a study that proves that changing the oil more
frequently than the manufacturer's recommendation will allow an engine to
last longer - if it's so simple, and, as you say, "not a
subjective/opinion/x/y axis answer", there must be objective data that
proves this.

With this information, maybe we can settle this issue once and for all.

Thanks,

Jim Ochi
jochi@domain.elided

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