Thicker oil better for engine start up?

[Shannow]

So there are two scenarios to consider, and consider all the above events in sequence.

Take my place...Australia
The oil is pumpable, to the extreme.
Turn the key, cranks easily
Engine starts, oil pumps straight away
Oil then "falls" into the pickup, ready to replace that pumped oil.
The oil rushes through the galleries, pushed the air out, and gets oil pressure established globally.
In the meantime, the pistons and bearings have yesterday's oil on them, and haven't noticed a thing with that 10 times operational viscosity oil holding them apart.

I can run 20W anything, SAE30, or 0W anything and have no impact on the above.


Take some place that recently got to -40C
Turn the key - the CCS is needed, or it won't start
Once it starts, you need the MRV to get the oil moving.
Oil pump relief is probably tripped, the galleries fill slower than mine.
The oil takes longer to fill the galleries and get to all places
The bearings and pistons HAD a lot of oil to start with, but 10 seconds is about the residence time, hope the oil gets there before they run out

Get the wrong oil, and get a badly broken engine.

That's where the W rating comes in.

That's what the Esso videos are showing...the wrong oil at low temperatures is VERY bad.

They do not show that a 0W at 32F pumps better.

shows that at different temperatures, differnt "W" ratings do the same job at getting the oil where it needs to go. Once it's all pumpable, they are essentially equal.

 

[NGRhodes]

Originally Posted By: Ducked
Originally Posted By: NGRhodes
http://www.emeraldinsight.com/doi/pdfplus/10.1108/00368790010352691

"This study has demonstrated a correlation between relative average cylinder liner wear rates at low engine start-up temperatures, base oil composition and oil viscosity"

Emphasis mine.


So I have to pay 32 USD to read that and then if I'm convinced I have to buy "full synthetic SAE 5W40 grade oils based on Polyalphaolefin"", and a diesel truck.

Ooer! Just as well cold starts mean 10C here.


Engine Test procedure

"measurements were performed by AEA at
Harwell using a germanium spectrometer"
"Five cold/hot start engine test cycles were
run on each test oil"
"data measured for each of plotted as cumulative wear against each
appropriate cold start cycle"
"Differences greater than 10 per cent in the
relative average wear rate can be regarded as
significant. For each test oil, no additional
wear was detected after the five hot engine
start test phases."

Relative cold start wear rates (-21C) vs. CCS viscosities of test oils at -21C

Relative cold start wear rates (-21C) vs. scanning Brookfield (SB) viscosities of test oils at -21C

Relative cold start wear rates (-21C) vs. time (secs) for initial oil gallery pressure rise at -21C

Relative cold start wear rates ( -26C) vs. CCS viscosities of test oils at -26C

 

[Shannow]

Good stuff...




but their "correlating wear" to every other parameter is a bit specious.
e.g. the first three charts...

Are they corellating the wear with
CCS
MRV or
GAllery filling time.
W
When it seems just the "W" grade at -21C is the determinant.

Then the CCS within the 5W40 grade at -26C, the "relative" wear takes out the real life component, and really, there's only 2.3% CCS diffence in the fist two, while the chart tries to show a linear type correlation