It's common knowledge in the VW/Volvo diesel community that when you get
an abused engine that has stuck rings and low compression from running
non-diesel rated oil, a few thousand miles on Mobil 1 can often clear up
the rings, and return the engine to normal compression and oil
consumption. I assumed that the same is probably true for all diesel
engines with piston rings when I made the comment before. While my
experience is consistent with this, I don't understand the underlying
mechanism at work here.
As a scientist I'm always frustrated by opinions and common knowledge on
engine oil, because everyone has conflicting ideas they stand by
religiously, and nobody has any scientific evidence or rationale for any
of them- myself included.
When I get an old diesel that was invariably run on regular cheapo dino
oil, I run Mobil 1 Turbo Diesel Truck, and the oil consumption and smoke
go down after ~10k miles or so. It could also be because I run the
engines hard and do mostly high speed freeway driving just as much as it
could be the oil.
Tyler
Curt Raymond wrote:
Well none of that makes any sense to me at all...
I've personally seen Mobil 1 10w30 free up carboned rings in a lawn tractor. I
have actual proof, pre-Mobil 1 it was getting about 85# compression, after
mowing with Mobil 1 in the crankcase for about 4 hours (getting it good and hot
and letting Mobil 1 do its thing) we were up to about 95#. That doesn't sound
like a big increase but it made the thing start way easier and it was noticably
more powerful.
I agree that thinner oil will help remove carbon and sludge but I fail to see
why synthetic oil with its greater detergent levels wouldn't do the job, you
could get 0w20 Mobil 1 for instance...
-Curt
Date: Sun, 10 May 2009 21:52:56 -0400
From: Steve MacSween <steve.macsw...@videotron.ca>
Subject: Re: [MBZ] Doing SVO Wrong
To: Mercedes Discussion List <mercedes@okiebenz.com>
Message-ID: <c62cfd38.189ff%steve.macsw...@videotron.ca>
Content-Type: text/plain; charset=US-ASCII
Race engine builders recommend that to free up sticky rings, use the
thinnest oil you can for as long as the engine will stand it (even if that
is 20 minutes).
The same additives in synthetics that add to synthetics' slipperiness, tend
to worsen the ring sludge.
I started asking about this after I had to give up on an OM616 with one or
two sticky rings, about three weeks after switching to Mobil 1. The smoke
got slowly worse by the day as soon as I switched over.
We have a rally engine builder locally and that is who I got the answer
from.
Mac
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