Originally Posted By: SubLGT
Originally Posted By: pipo
.........Is this perhaps a prescription for fresh oil just before the start of the coldest months in cold weather climates?
Yes. See this paper from Infineum: "Assessment of Ageing Mechanisms in Lubricants and Their Effects on Retained Low Temperature Pumpability of Top Tier Oils"
http://www.infineum.com/Documents/Crankc...icants-2010.pdf
I have taken the liberty of excerpting below a few paragraphs from this paper. One thing I have definitively decided is that blending oils to reduce the low temperature pumping viscosity is a fool's errand, and might actually have the opposite effect due to unforseen interactions of the various oil components. Also, using fresh oil at the beginning of winter and shortening the oil change interval in winter are likely to help maintain the oil's low temperature pumpability. Finally, does anybody know which oils use crystalline viscosity modifier (VM) chemistries, such as
HE-OCP, which apparently are more prone to adverse ageing and low temperature pumpability problems?
"oil can undergo a number of changes during its lifetime in the
engine which adversely affect low temperature pumpability.
Industry stakeholders are now expressing concerns about the
potential risk of engine failures due to deterioration of low
temperature pumpability of oils during their life cycle in the
engine. Concerns have also been raised over the last few
years that the move to Group III base stocks, while improving
many of the properties of oil formulations, may also impact
their retained low temperature pumpability.
The oil in the engine is exposed to a variety of
processes, such as (a) oxidation, nitration and thermal
degradation; (b) mechanical shearing; (c) evaporation; (d)
contamination with combustion by-products; and (e) comingling
with fuel and top-up oils. These processes can have
profound effects on the pumpability of the oil, potentially
leading to catastrophic lubrication failure.
mixing two
well performing oils, commonly known as top-up, can result
in a lubricant mixture failing low temperature pumpability
oils blended
with crystalline viscosity modifier (VM) chemistries, such as
HE-OCP, were much more prone to loss of pumpability upon
ageing than other VM chemistries.
some formulation
decisions, such as the choice of viscosity modifier in
European formulations, have been shown to move a
formulation with a strong additive system into the failing
aged oil pumpability regime
In the
current formulating environment, when interactions of all
lubricant components are carefully balanced, it is particularly
important to understand ageing mechanisms and their effect
on this intricate balance. The importance of such
understanding was demonstrated by analyzing the causes of
low temperature pumpability field failures which resulted
from the formation of a waxy, quasi-solid gel. The ageing of
the oil in this case was not particularly severe with mild
oxidation and a low level of biodiesel fuel dilution. But these
ageing routes led to a change in the interactions between
additive package components, base oil, viscosity modifier
and pour point depressant. These interactions resulted in
apparent gel formation and loss of low temperature
pumpability in field service. Ageing of the oil in service can
have a profound effect on low temperature pumpability."
