Start up protection differences - 10w, 15w, 20w?

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How different is cold start-up flow/protection in a 10w-30 versus a 15w-40, versus a 20w-50?

Assume we're starting above freezing (vast majority of the time). Does the 10w circulate faster such that it reduces wear on start-up over the other two?
 
Originally Posted By: OceanRuns
How different is cold start-up flow/protection in a 10w-30 versus a 15w-40, versus a 20w-50?

Assume we're starting above freezing (vast majority of the time). Does the 10w circulate faster such that it reduces wear on start-up over the other two?


No

the "w" is the extreme end of the cold performance test.

Above freezing, your pump will move the same volume of oil to purge the galleries of air.

Wear occurs during the warmup phase, when typically the oil is there, pressurised, and flowing.
 
Originally Posted By: Shannow
OceanRuns said:
Above freezing, your pump will move the same volume of oil to purge the galleries of air.

Wear occurs during the warmup phase, when typically the oil is there, pressurised, and flowing.


So, to understand, is there a difference in the wear protection between the three during warm-up? (Above freezing external temp.)
 
Unlikely, although if it's an ILSAC 10W30 (or SN/SM versus SL), it will have a lower high shear rate viscosity, and a lower additive level than the other two.
 
Originally Posted By: Shannow
Unlikely, although if it's an ILSAC 10W30 (or SN/SM versus SL), it will have a lower high shear rate viscosity, and a lower additive level than the other two.


are you talking VII?
 
No-SN limits ZDDP levels to protect catalytic converters in 10W30, 15W40 & 20W50 can have much higher levels & still meet SN (although some HM oils are actually rated SL).
 
Originally Posted By: OceanRuns
Assume we're starting above freezing (vast majority of the time). Does the 10w circulate faster such that it reduces wear on start-up over the other two?


Nope
 
Originally Posted By: BrianC
As a general rule, the lower the first #, the better the start up performance at any temp.


How does that work ?

If you use the example of M1 0W30 verus 5W30, the viscosities are near identical from freezing up...the 0W CAN'T be better.

Use any other oil within reason above it's extreme limits of pumpability, and the pump moves the same volume per rev regardless to fill the galleries.

So how does a 0W "generally" perform better at any temp ?
 
Originally Posted By: BrianC
As a general rule, the lower the first #, the better the start up performance at any temp.


I would clarify/qualify that by saying "for a given viscosity when speaking of the multigrade characteristics, the lubricant with the lower number in front of the W will generally thicken less as cooled."

Of course there are exceptions to this and as Shannow noted, it is of questionable significance until we approach the CCS/MRV limits for the grade(s) in question. And also that by "performance" we are speaking specifically as to the oil's ability to resist thickening.
 
I have noticed many have crossed the thinner at start up to equate to the thinner oil will have less wear at start up. I haven't seen a shred of evidence for that, though thinner oil will definitely start easier when it's cold out.

I am actually running straight 30 right now in the Jeep, and at late spring temperatures I can't tell a whit of difference in the way the Jeep starts over the usual much thinner 10w30. FWIW.
 
The oil can not circulate faster, oil pumps have a fixed displacement, and oil is not really compressible.

The question is: Will a thicker oil provide better protection during the first 10 minutes after start up?

Or:What effect will Light or Heavy 'residual' oil from a previous run, have on engine wear during the first 20 seconds* of a cold start.

*Or whatever time it takes for oil to circulate in an engine
 
Originally Posted By: OVERKILL
Originally Posted By: BrianC
As a general rule, the lower the first #, the better the start up performance at any temp.


I would clarify/qualify that by saying "for a given viscosity when speaking of the multigrade characteristics, the lubricant with the lower number in front of the W will generally thicken less as cooled."

Of course there are exceptions to this and as Shannow noted, it is of questionable significance until we approach the CCS/MRV limits for the grade(s) in question. And also that by "performance" we are speaking specifically as to the oil's ability to resist thickening.


Exactly

This nonsense that a 0w-xx will pump faster at start up seems to get said often however because oil pumps are positive displacement it doesn't matter if you've got a 0w-20 or a straight 60 grade in the sump because the oil pump will push the same volume of oil either way.
Pressure is affected in that the thicker product is more resistant so there will be an increase in drag which may affect fuel consumption as well as starting.
As we've come to learn it's not the starting of a cold engine that contributes the most to wear,it's the warming up of the oil,so thicker oil may contribute to longer Intervals of hydrodynamic lubrication which eliminates metal contact rather than depending on the additive package once the oil has thinned enough.
 
The starting viscosity is most important when considering how long the time it takes to travel from the sump to the oil pump. Start up wear is a complicated issue With many things causing the higher wear. For example a colder engine needs a richer air fuel mixture to start and run. The pistons are oval when cold ,measure them ! they round up when heated.. The clearances are larger which causes more wear until they parts expand ETC. ETC.
 
Originally Posted By: CT8
The starting viscosity is most important when considering how long the time it takes to travel from the sump to the oil pump.


Which is what the MRV test is for.

The rest of your post is in-line with what Clevy noted.
 
Originally Posted By: expat
The oil can not circulate faster, oil pumps have a fixed displacement, and oil is not really compressible.

The question is: Will a thicker oil provide better protection during the first 10 minutes after start up?

Or:What effect will Light or Heavy 'residual' oil from a previous run, have on engine wear during the first 20 seconds* of a cold start.


*Or whatever time it takes for oil to circulate in an engine


What are the answers?
smile.gif
 
Originally Posted By: Clevy
Originally Posted By: OVERKILL
Originally Posted By: BrianC
As a general rule, the lower the first #, the better the start up performance at any temp.


I would clarify/qualify that by saying "for a given viscosity when speaking of the multigrade characteristics, the lubricant with the lower number in front of the W will generally thicken less as cooled."

Of course there are exceptions to this and as Shannow noted, it is of questionable significance until we approach the CCS/MRV limits for the grade(s) in question. And also that by "performance" we are speaking specifically as to the oil's ability to resist thickening.


Exactly

This nonsense that a 0w-xx will pump faster at start up seems to get said often however because oil pumps are positive displacement it doesn't matter if you've got a 0w-20 or a straight 60 grade in the sump because the oil pump will push the same volume of oil either way.
Pressure is affected in that the thicker product is more resistant so there will be an increase in drag which may affect fuel consumption as well as starting.
As we've come to learn it's not the starting of a cold engine that contributes the most to wear,it's the warming up of the oil,so thicker oil may contribute to longer Intervals of hydrodynamic lubrication which eliminates metal contact rather than depending on the additive package once the oil has thinned enough.


So, if I understand this correctly, a 10-30w oil would warm faster, and thus provide more protection (and less wear), than a 15w-40/20w-50? Is that right? Or, do I have it completely wrong?
 
A positive displacement oil pump will pump various vis oils at the same rate(volume), but higher vis oils(30-40-50wt) require more energy to pump the oil than say a 0-20 will. Also the higher vis oils produce more heat, when pumped, than a lower vis oil.
 
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