Dave M. wrote:
In addtion to what Jeff said...
1) Marshall noticed that his OM60x engines would develop lifter noise
before a 5kmi change interval rolled around, which would go away when
the SynTec was changed. Reverting back to Mobil-1 kept them quiet past
5kmi. This was, I believe, with the original 5W-50 variety. Marshall
can correct or elaborate on this I'm sure.
Actually I noticed that SynTec consumption rate increased starting at
about 2500 miles. This is a CLASSIC sign of viscosity improver
(additive) breakdown (it happens with MANY conventional oils -
especially those that use ONLY group I base so must make extensive use
of viscosity improvers). At about the same time I was puzzling over the
increasing oil consumption rate, Red Line published a test in which an
unnamed 5W-50 oil (SynTec was the ONLY 5W-50 oil sold in the US then)
displayed marked reduction in lubricity that corresponded with the
increased consumption rate I was seeing. It was later confirmed that the
5W-50 oil was SynTec. As long as SynTec is changed frequently, it's
pretty good oil - much better than most conventional oils - but it
needed to be changed MUCH more frequently than Mobil 1 - long before
soot or other combustion by-products made it unsuitable.
2) IMO, almost all the "synthetic" oils on the shelf at McParts are
the fake Group III stuff (Rotella Syn, Valvoline, etc). There are not
many true synthetics left, but at the moment Amsoil, Mobil, and Red
Line are all the real deal. For more than you EVER wanted to know
about oils (and I'm not joking here), check out this website:
http://bobistheoilguy.com/
For the record I don't believe in any oil additives and the site above
basically agrees with that. For 1-time cleaning purposes, AutoRX is
neat stuff but that's not a magical additive like most claim to be -
it's specifically for cleaning. Neat stuff actually.
I use Mobil 1 for cleaning. Works GREAT. If an engine is spectacularly
dirty I have used a short interval (400-600 miles) of a high quality of
conventional oil with a VERY aggressive additive package (like Delo 400)
before putting in the Mobil 1 (but I only did that once and I'm NOT sure
anything was any cleaner at the first Mobil 1 change then with just
using Mobil 1 alone).
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 181Kmi,'87 190D 2.5 199Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
159Kmi, '87 190D 2.5 turbo 234kmi
Diesel Technical Advisor MBCA, member GWSection
http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
