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, Sat, 28 Oct 2000 05:24:07
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Adam -
When I was in school studying chemistry (awhile back, I must admit)
we had a seminar from the Quaker State people on the state of modern motor oil formulation. As I remember it, the viscosity adjusters were terribly long polymer chains which were coiled up when cold and streched out when long to provide the viscosity changes.
The problems which existed with these chains at that time were primarily
mechanical shearing of the chains due th their long (MW = 30k?) length. I don't think ther were very volatile.
Some cars tend to break up these chains much faster than others. For example my old Alfa which *ate* motor oil viscosity enhancers in 3k miles versus my TR-4 didn't seem to touch them. (FWIW, I cound Castrol to be about the longest lasting of the fossil oils) This also matches with the bad experiences reported in the Townsend site on 20W50 in Volvos (et al) - tho I strongly suspect that 20W50 is just fine if you change it every 5k or so).
I don't know what a Saab engine does to oil (since they don't have oil gauges), but I suspect its hard on the viscosity enhancement component with high temperatures, close tolerances and high RPMs. I always changed the fossil oil in my 2 liter non-turbos every 3 - 5 k and had zero problem. But I think the 9000's 2.3 l turbo engine demands more.
Based on this information I decided to stick with 10W30 Mobil-1 (w an oversize Mobil-1 filter) and change at moderate (5k) intervals mostly as a function of staying "within the envelope" of the life of the oil additive package, which is the typical limiting factor.
I'll ask around and see what is shaking in this field, I may still have a few connections.
, Sat, 28 Oct 2000 06:00:11, Sat, 28 Oct 2000 05:24:07, Sun, 29 Oct 2000 15:02:28
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