Originally Posted By: hamm
but thinner oil means more wear specially in a hot temp , air con and traffic ... right ?
Yes, you are right as above statements had been properly peer-reviewed by professionals in SAE, API , AECA, Universities etc .......
in relation to which any so called 'peer review', if any which it doesn't , from OEM marketing propaganda and Bitog should be taken with a heavy pinch of salt or ignored, provided it's peer-reviewed typically by Universities .
Hot oil temperatures , in itself does not cause abrasion and adhesion wear.
However it reduces oil operating viscosity and it's inching towards propensity for increased abrasion and adhesion wear.
So is reduced operating viscosity, in itself does not cause abrasion and adhesion wear.
However it reduces oil film thickness and further inches towards propensity for increased wear, further reducing your 'margin of safety' so to speak.
Going forward, reduced operating viscosity (other than increased engine load and reduced engine speed ) that causes reduced oil film thickness, and at a particular magnitude of surface roughness of mating surfaces, gives rise to a (new) phenomenon of shifting lubrication regimes from:
a )Hydrodynamic Lubrication (HL) regimes to Elasto Hydrodynamic Lubrication (EHL) regimes; and from
b )EHL regimes to Mixed Lubrication (ML) regimes ; and from
c )ML regimes to Boundary Lubrication (BL) regimes, ultimately.
Adhesion and abrasion wear would definitely increase further in scenarios (b) and (c) above, though 'usual' lubricant oil contamination level can too results in abrasion wear in (a) above.
Now, it's the increased adhesion and abrasion wear , which often are localised at contacting surfaces AND
alters dimensions and surface roughness of individual contacting components to the extent it's sufficient to .........
alter the 'design and mechanics of components operation of said engines' ,
that plays a major role in reduction of components longevity.
SAE paper(s) did suggest that majority of engine wear is corrosion wear, especially at startup and warmup phase or 'short' period after fully warm up phase.
They are influenced by among others cold oil (and ambient) temperaturess, some (or all) biofuels , fuels additive and engine oil additive packages, driving patterns etc.
However, with improved quality of current day fuels/oils and in relations to (localised) adhesion and abrasion wear,
I'm personally not quite worried about corrossion wear (which constitutes majority of engine wear) for the following reasons, namely:
a) they are not localised generally; and
b) where localised corrossion wear does occur , they are not at the contacting surfaces ; and
c) where corrosion wear occurs and localise at a certain pair of contacting surfaces (which I'm highly doubtful of ), it's likely spread out along the surface profiles of contacting components ........
such that all 3 scenarios above are not likely to result in changes in (measurable) components dimensions (in microns or a fraction of a thousandths of an inch) ---
hence, its (meaning corrosion wear) effect on reduction of engine components longevity is insignificant AND inconsequential , if any.
