Cold Start wear studies

[Albs]

Hello there, not the most original thread out there I know, but I tried hard in searching the exact same take on this matter without luck.

Beside the obvious (that a 5w or 0w have similar performances starting from cold over 0°C) I assumed that a lower weight (w20 over w30), and so lower HTHS offered a greater protection in the first minutes of starting from cold due to the higher pumpability provided the lighter grades.

I found this recent publication from Boris Zhumd in 2021, and it seems like a higher viscosity (thus hths) oil protect more in similar scenarios like "start-stop".
The study lacks results in a "cold start" scenario. Are my previous assumptions wrong? Will a higher HTHS protect more in the early stages of engine start-up to fully in temperature than a lower one?

 

[Jetronic]

Mr Zhmud is a member here. You could possibly ask him directly, or look at the collection of publications on Bizol's website

https://www.bizol.com/products/research-development/

But in short, once an oil is pumped succesfully, there's no improving the protection. The higher viscosity that increases the power needed to pump also reduces the oil "loss" from pressure fed lubricating surfaces so less oil is actually needed to replace it.

 

[Albs]

Thanks for the hint Jetronic, I'll try and ask him directly. In the meantime I would gladly accept explanation from whoever has it

 

[FowVay]

Scroll through the articles that are offered under the link from Jetronic. There is one dated 2018 titled "Viscosity Matters". In this article it is addressed the benefits of the HT/HS viscosity measurement. Note that this is taken at a higher temperature (150ºC) and is a dynamic measurement as opposed to the lower kinematic viscosity that is measured in centipoise and taken at 100ºC. This equates to the HT/HS viscosity being highly relevant when considering bearing temperatures.

A cold-start/dry-start situation would negate the importance of a high HT/HS viscosity. What does matter is pumpability AND the chemical additives required to provide boundary layer protection prior to the oil reaching operating temperature.

There are several excellent articles written on this page and I am thankful to have been shown this link.

 

[Cujet]

I found the article interesting. Also of note are various tests that show engine components can be, and sometimes are, manufactured for very low rates of wear with very low viscosity oils. Unfortunately, we tend to consider a car with 200K miles as "worn out" and disposable, and it seems acceptable to have worn out engines around this time. Even the Prius tends to consume oil about this point.

 

[bbhero]

^^^^^^^^^^^^^^^^^^^^^^

Very, Very good post in my opinion.

 

[ZeeOSix]

You don't want oil starvation at cold start-up, as starvation is lack of lubrication which leads to wear and/or damage. In very cold temperatures using the correct W rating is key to ensure proper pumpability by the positive displacement oil pump so oil gets pumped and distributed quickly. As long as the oil is completely pumpable then all forced lubrication should be adequate. If the oil is too cold and thick to properly pump, then flow starvation will occur, and the longer that happens the more wear there could be as the leftover oil film between moving parts can only last a short time to protect moving parts.

With adequate pump flow as discussed above, "start-up" wear has more to do with parts rubbing together before enough relative motion between parts can produce adequate hydrodynamic or mixed boundary lubrication. The journal bearings are rubbing together for a short time when the engine is cranking over before it fires up and hits idle RPM. There will always be an oil film on parts, so wear from boundary lubrication will be prevented for a short time by the existing film through the AF/AW additives (oil film strength). It can only last a short time, so oil flow needs to show up relatively quickly to all moving part.

I think engine wear from inadequate hot viscosity and HTHS is a bigger factor than cold start-up assuming correct W rating for the use conditions. Inadequate viscosity/HTHS is also influenced by oil health due to vehicle use condition, like the mileage on the oil, amount of fuel dilution (viscosity shear and reduction) etc. So in other words, an adequate OCI and filter efficiency are also important factors to maintain oil viscosity and cleanliness to control engine wear.

 

[ChrisD46]

*My "cold start oil elixir" is adding 16 oz. ~ 32 oz. of Castrol Magnatec (5W20 / 5W30) to my new synthetic oil fill ... My butt dyno and ears can can actually hear and feel the Magnatec oil molecules clinging to metal at the start of an OCI when added as I have done . *Butt dyno / hearing sync up is an aquired art - it takes a while to master the process !

 

[BMWTurboDzl]

Question. As I understand it oil weight has no bearing on how quickly a positive displacement oil pump transports oil from the oil pan to the valve train however doesn't oil weight impact the rate at which oil spreads out across the valve train itself?

https://www.bimmerpost.com/goodiesforyou/N55-guide-BIMMERPOST.pdf (see pgs 53-60)

 

[Snagglefoot]

I’m not going to comment other than post this recent ad from Exxon Mobil. Exxon has researched this extensively.

 

[ZeeOSix]

Question. As I understand it oil weight has no bearing on how quickly a positive displacement oil pump transports oil from the oil pan to the valve train however doesn't oil weight impact the rate at which oil spreads out across the valve train itself?

Yes, but I would think that the "W" rating also takes that factor into account. Maybe instead of just a "W" rating, the oil bottles should also have a "Minimum Use Temperature" listed.

 

[tig1]

I found the article interesting. Also of note are various tests that show engine components can be, and sometimes are, manufactured for very low rates of wear with very low viscosity oils. Unfortunately, we tend to consider a car with 200K miles as "worn out" and disposable, and it seems acceptable to have worn out engines around this time. Even the Prius tends to consume oil about this point.

I noticed you comment about "worn out engines", and I would agree for the most part. However my 2007 Ford Fusion 2.3 now has 279K and still performs great with no oil consumption in my normal 10k OCI using 20 wt oil. M1 oils of course.

 

[tig1]

Question. As I understand it oil weight has no bearing on how quickly a positive displacement oil pump transports oil from the oil pan to the valve train however doesn't oil weight impact the rate at which oil spreads out across the valve train itself?

https://www.bimmerpost.com/goodiesforyou/N55-guide-BIMMERPOST.pdf (see pgs 53-60)

 

[wpod]

Question. As I understand it oil weight has no bearing on how quickly a positive displacement oil pump transports oil from the oil pan to the valve train however doesn't oil weight impact the rate at which oil spreads out across the valve train itself?

https://www.bimmerpost.com/goodiesforyou/N55-guide-BIMMERPOST.pdf (see pgs 53-60)

What about the time it takes for the oil to get from the sump to the oil pump? If we want to break up cold starting oil flow into parts. What would a straight 30 oil flow look like at 50* F starting temps?

 

[wpod]

I noticed you comment about "worn out engines", and I would agree for the most part. However my 2007 Ford Fusion 2.3 now has 279K and still performs great with no oil consumption in my normal 10k OCI using 20 wt oil. M1 oils of course.

We look at engines full of sludge and think syn oil, syn oil the nectar of the chosen ones not thinking the engine has had only 2 oil changes in the past 80,000 miles.

 

[BMWTurboDzl]

What about the time it takes for the oil to get from the sump to the oil pump? If we want to break up cold starting oil flow into parts. What would a straight 30 oil flow look like at 50* F starting temps?

Doesn't the oil pump remain primed?

 

[ZeeOSix]

What about the time it takes for the oil to get from the sump to the oil pump? If we want to break up cold starting oil flow into parts. What would a straight 30 oil flow look like at 50* F starting temps?

Don't rev the engine to near redline with very cold oil and a small sump capacity if you're worried about it not draining back down to the sump fast enough. Straight 30 weight doesn't flow that bad at 50F. Maybe so at 0F and below. There's a reason that muti-weight oils and the "W" (Winter) ratings were invented. It sure wasn't for the use of the oil when it's fully hot.

 

[sk_pete]

I found the article interesting. Also of note are various tests that show engine components can be, and sometimes are, manufactured for very low rates of wear with very low viscosity oils. Unfortunately, we tend to consider a car with 200K miles as "worn out" and disposable, and it seems acceptable to have worn out engines around this time. Even the Prius tends to consume oil about this point.

hmm. oils have less saps, longer oci, than 20-30years ago. (i think less cleaning power)
could it be, all problems are related to dirt accumulation ?

 

[PimTac]

hmm. oils have less saps, longer oci, than 20-30years ago. (i think less cleaning power)
could it be, all problems are related to dirt accumulation ?

Isn’t that what the filter is for?

 

[sk_pete]

i think amount of "coal" on pistons etc, is getting worse than ever before.
now this lspi thingy-> goodbye calcium, they say it has best cleaning power. longer oci not making situation better.
do i understand this correctly?