Heavier oil weights in hot climates??

[dlundblad]

Originally Posted By: Ken2
Quote:
if I drove say an oil consuming Chrysler 3.8
Why is it consuming oil? Glopped up PCV? Thicker oil isn't the answer. Carboned piston rings?--not the best answer. Leaking valve seals?--not the best. Leak when driving?--little or no help. Worn piston rings?--rare these days, but now thick oil is a help.


3.8's are known to consume oil. Worst case scenario is about 1 quart per 1000 miles. A quick search will explain better than I can.

 

[285south]

Originally Posted By: tig1
Two things.

1) It doesn't get all that hot in Florida.

2) 20wt oils perform very well in all air temps.


#1 is very true. Hot Atlanta and Florida do not even come close to Phoenix. In Phoenix you can cook eggs off the pavement and at night it is a cool 95*F.

I recommend 10-30. My neighbors all used 10-30 year round for many many years, it held up, and don't use 10-40 or 20-50 in their vehicles.

I yell at people when they walk their dogs during the day. Sure you might have on shoes, not feel how hot the pavement is on your feet, but your dogs sure do you pinhead. Unfortunately its the only way to correct stupid behavior.

 

[Errtt]

My DD OM says I can use 5w30 in higher temps when normally it specs 5w-20. Nothing about consumption.
So I use 5w-20 in the winter, then 5w30 all other times, and we regularly see triple digit temps during summer.

 

[CATERHAM]

Originally Posted By: Shannow
10cst will always provide a greater parts separation than 7cst...

whether that provides more protection is debatable, as the later may or may not be operating in boundary lubrication conditions somewhere in the engine (maybe in a nook/cranny). If it is, then the thicker oil will provide greater protection.

Given that the thermostat and cooling system control the viscosity at the operational temperature of 100C give or take, then 7 or 10 means nothing in terms of wear, but which has more margin for error...the thicker having more margin, always.

What the higher ambient always does is remove any need to chase VI for engine protection. You may choose to choose increased VI for tinily better warmup fuel economy, and great.

Not needing to chase VI meand that you can choose an oil that is more predictable in terms of viscosity retention, and volatility over the OCI...so yes, I agree with your last para.

A lot old school misconceptions here.
Firstly, having a thicker viscosity margin than necessary is counter-productive in terms of both lubrication and engine efficiency.
Secondly, high VI oils are not necessarily more prone to viscosity loss than lower VI oils.
Thirdly, the advantages of a high VI are not only a lower cold start-up and warming-up viscosity but high VI oils also retain more of their normal operating viscosity at very high oil temp's. Consequently you are maintaining a greater viscosity safety margin with high VI oils for a given normal operational viscosity.
Not surprisingly, the most advanced race oils are high VI 0W-XX grades.

 

[HTSS_TR]

Originally Posted By: CATERHAM
Originally Posted By: Shannow
10cst will always provide a greater parts separation than 7cst...


A lot old school misconceptions here...

 

[turtlevette]

Originally Posted By: Shannow
10cst will always provide a greater parts separation than 7cst...


Then 20cst will provide a thicker film than 10cst. Or 30cst. Let's just pack the crankcase with grease.

 

[hatt]

Originally Posted By: turtlevette
Originally Posted By: Shannow
10cst will always provide a greater parts separation than 7cst...


Then 20cst will provide a thicker film than 10cst. Or 30cst. Let's just pack the crankcase with grease.




LOL. Technique number 1, The Art of Controversy.

 

[fdcg27]

Once the thermostat is fully opened and the electric fans are running, the liquid cooling system ceases to prevent increases in engine temperature, although in most modern vehicles the cooling system is very efficient and will prevent overheating under any ambient conditions anywhere.
Oil grades?
You could use a thicker grade all year 'round in a place that never sees real cold.
It might help to reduce consumption.
Most engines are sold in a variety of markets and we've seen many threads in which much thicker grades are recommended for any given engine in any given market, so thicker grades apparenlty do no harm.

 

[Shannow]

Originally Posted By: CATERHAM

A lot old school misconceptions here.
Firstly, having a thicker viscosity margin than necessary is counter-productive in terms of both lubrication and engine efficiency.


Won't argue on the latter, as it DOES consume tinily different amounts of fuel...interested in how greater part separation is counter productive to "lubrication"...cite sources please.

Originally Posted By: CATERHAM
Secondly, high VI oils are not necessarily more prone to viscosity loss than lower VI oils.


Doesn't your own Vauxhaul viscometer tell you that TGMO sheared to 2.4HTHS in less than 200 miles ?

I mean it's the most advanced engine oil in the world, and your own testing showed a marked operating viscosity loss, actually taking it out of grade in less than 200 miles...if it indeed started in grade, as you've recently posited.

Originally Posted By: CATERHAM
Thirdly, the advantages of a high VI are not only a lower cold start-up and warming-up viscosity but high VI oils also retain more of their normal operating viscosity at very high oil temp's. Consequently you are maintaining a greater viscosity safety margin with high VI oils for a given normal operational viscosity.


You haven't demonstrated yet that VI relates to HTHS, however, I'll demonstrate relateively simply for you.

A Newtonian SAE 30, with a viscosity index of 100 will have an "operating" viscosity of 3.5 at 150C, it's HTHS and KV150 will basically be the same, at 3.5

a 5w30 (and I'll use your "typical" 5w30, not the ones that you would posit are really 40s) will have an operational viscosity (HTHS) of 3 at 150C.

As you correctly point out, time and time again, operational viscosity is HTHS, so the lowly 100VI SAE 30, which is the true definition of being a 30 has a higher viscosity safety margin than the 5w30.

Where, between 150C and (maybe) 200C does the 5w30 catch up and overtake ?

Sounds like the extreme end of overheating, and as you have continually pointed out to me, the reliability of cooling systems and lubrication systems these days is such that extra headroom just simply isn't needed (I disagree with you, but respect your argument).

 

[CATERHAM]

The latest version of TGMO 0W-20 (VI 215-235) has been proven to be more shear stable than M1 AFE 0W-20 (VI 173).
Sustina 0W-20 (VI 229) has also proven to be very shear stable.
Shear stability is oil specific and choosing a lower VI oil doesn't guarantee shear stability so drop the oil school assumption, it doesn't apply today.

And yes it's a fact, higher VI oils provide greater high temp' protection for a given normal operational viscosity; they simply do not thin out at the same rate. I've observed this myself with the different oils I've tried and race oil formulators emphasis the point as well; Joe Gibbs Driven comes to mind.

 

[Shannow]

Originally Posted By: CATERHAM
And yes it's a fact, higher VI oils provide greater high temp' protection for a given normal operational viscosity; they simply do not thin out at the same rate.


Would be very interested in some actual data on this, particularly given that the VI is based on KV40 and KV100, and boosted by VIIS...and the HTHS is when the VIIs are "flat" for want of a better word in temporary shear.

So you are asserting that they are still functioning as VIIs in the second newtonian phase, and this creating a high shear "viscosity index".

Not doubting, just would like to see some science to back the fact that when they aren't functioning as VIIs, they are...

 

[Merkava_4]

Originally Posted By: dlundblad
The way I see it, thicker weights aid consumption.. not offer better protection in heat. Am I correct?


Thicker weights do a lot more than just reduce consumption, they also lubricate better. Oils get thinner and thinner as they get hotter. You get 5W-20 up to 212 degrees Fahrenheit, you don't have much of a film left.

 

[gfh77665]

One thing that no one can deny:

20wt. = CAFE,........... not maximum engine protection in the heat.

CAFE is why they are here.

 

[edhackett]

Originally Posted By: Shannow
Originally Posted By: CATERHAM
And yes it's a fact, higher VI oils provide greater high temp' protection for a given normal operational viscosity; they simply do not thin out at the same rate.


Would be very interested in some actual data on this, particularly given that the VI is based on KV40 and KV100, and boosted by VIIS...and the HTHS is when the VIIs are "flat" for want of a better word in temporary shear.

So you are asserting that they are still functioning as VIIs in the second newtonian phase, and this creating a high shear "viscosity index".

Not doubting, just would like to see some science to back the fact that when they aren't functioning as VIIs, they are...


I've wondered at what temperature the VII become ineffective. At some point they are fully "uncoiled" and the oil will become newtonian in response to temperature. I would really like to see actual viscosity measurements taken every 5 degrees C from 40C to 200C.

"Flat" VIIs still have some effect on viscosity, but at some point they will be totally ineffective and the oil will not respond as predicted by the VI.

Ed

 

[ueberooo]

Originally Posted By: gfh77665
20wt. = CAFE,........... not maximum engine protection in the heat.

CAFE is why they are here.


Well said; I believe that's true often. A good auto maker will list all recommended or compatible oil grades for a given temperature range. Depending on climate and when in the season you are changing the oil, select the thicker grade if you are going to be using it in hot climate. I probably wouldn't risk going with a higher visc oil that goes beyond compatible oils listed in manual, although it could have benefits; for a higher mileage car (>200,000 km), I might give it a try and see how it works, because the downside is smaller, and the piston/cylinder tolerances have widened.

Some people in this thread have commented to suggest that typical oil temps don't vary from season or climate in modern liquid cooled cars (just because they have thermostats, computers, and coolant pumps?); that doesn't show a lot of understanding of what goes on underneath, inside the coolant system; if you've ever changed a coolant pump, it runs directly off the crank or camshaft, with its pumping rate directly fixed to engine rpm. On a hot day, with electric fan running at full duty, that's as much cooling as you'll get.

Thanks to fdcg for pointing that out and correcting that:

Originally Posted By: fdcg27

Once the thermostat is fully opened and the electric fans are running, the liquid cooling system ceases to prevent increases in engine temperature, although in most modern vehicles the cooling system is very efficient and will prevent overheating under any ambient conditions anywhere.
Oil grades?

 

[Shannow]

Originally Posted By: hatt
Originally Posted By: turtlevette
Originally Posted By: Shannow
10cst will always provide a greater parts separation than 7cst...


Then 20cst will provide a thicker film than 10cst. Or 30cst. Let's just pack the crankcase with grease.

LOL. Technique number 1, The Art of Controversy.


I thought it was three in the handbook...

Translated, it's from ancient trollish for "I don't understand how grease works either"

 

[edhackett]

Here's a nice graph showing the effect of high shear on VIIs:

https://www.oronite.com/paratone/shearrates.aspx

Ed

 

[Shannow]

Originally Posted By: edhackett
Here's a nice graph showing the effect of high shear on VIIs:

https://www.oronite.com/paratone/shearrates.aspx

Ed


This one explains it some

http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf

and then demonstrates that the 10^6 shear rates obey the traditional log log behaviour...not a big jump, as Newtonian fluids have it.

Alas it stops short and doesn't do the comparison of what a straight versus multigrade oil does in the second newtonian phase wrt VI..obviously the High shear VI for the Newtonian is the same as the multigrade, not so sure about multis in high shear.

 

[jrustles]

Originally Posted By: Shannow
Originally Posted By: edhackett
Here's a nice graph showing the effect of high shear on VIIs:

https://www.oronite.com/paratone/shearrates.aspx

Ed


This one explains it some

http://www.savantlab.com/images/TBS_Paper_-_SAE_2008-01-1621_The_Expanding_Dimensions....pdf

and then demonstrates that the 10^6 shear rates obey the traditional log log behaviour...not a big jump, as Newtonian fluids have it.

Alas it stops short and doesn't do the comparison of what a straight versus multigrade oil does in the second newtonian phase wrt VI..obviously the High shear VI for the Newtonian is the same as the multigrade, not so sure about multis in high shear.


Haha Steve you cheeky bugger, still busting nuts like clockwork

Quality article. This part needs a little highlight:
Quote:

It should be noted that the level of force applied to create
such macromolecular orientation is usually far less than
the force necessary to break its molecular bonds. Thus,
the polymer coil recovers its shape when the shearing
force is relieved and the earlier viscosity level is
recovered. This response of a polymer-containing oil is
termed ‘temporary viscosity loss’ (TVL) and, for
comparison of TVL values, is often presented as %TVL.



To address the original post, I personally do not care to use a motor oil formulated with agents that aid in sub-zero oil flow during any such drain interval that sub-zero pumpability will not be encountered. I will only use such products when sub-zero cranking is expected. It's really quite simple IMO. Of course, this only speaks to VI or 'straightness', not 'weight'. Changing to heavier multigrades as a way to maintain durability/margin of error according to season/ambient is a crutch IMO. I would simply use a grade of the same viscosity that is of a more newtonian nature (ie less Poly VII's that introduce viscometric unpredictability under HTHS).

 

[Garak]

Originally Posted By: Shannow
What the higher ambient always does is remove any need to chase VI for engine protection. You may choose to choose increased VI for tinily better warmup fuel economy, and great.

I'd agree with this statement, and I'd even go further than that. Some of the arguments about the heat are a bit backwards.

First off, for those who are naysayers about 20 grades, do recall that SAE 20 was a summer recommendation at one time, long before CAFE was even considered. SAE 30 was common, too. Much rarer was the SAE 40, which was more commonly seen in diesels.

When you look back to the time when vehicles had these charts, the heaviest specified grades (i.e. a 20w-50 or an SAE 40) were not called for to respond to the heat, but allowable under hot conditions. Obviously, they didn't call for the old SAE 10w for a hot summer day; they wanted you to jump up in grade on that. Nonetheless, I can't think of any examples from the day that called for an SAE 30 on a moderate summer day, but insisted on an SAE 40 on a really hot summer day.

This is where I'm saying we have this backwards. Traditionally, it was important to choose an oil light enough to start in the coldest ambient conditions one would encounter during the OCI, not the hottest. One didn't start with an SAE 10w in the winter and switch it to SAE 30 half an hour down the road when the sump temperature stabilized.

There is very little need for seasonal viscosity switches, thanks to modern multigrades. Also, thanks to modern multigrades, there is usually no concrete reason to run a different viscosity in a place like Florida versus a place like here in the same application. Find something that will start in the winter and still have adequate viscosity at operating temperatures; that's usually what's shown in the manual. It's not much more complex than that.

One could run an SAE 30 in Florida. I could try an SAE 10w here in the winter. That doesn't mean either is a particularly good idea. I've been sticking to the same grade (be it a 0w-30, 0w-40, 5w30, or 5w-40, depending upon the application) as a year round oil choice, be it 100+ F in the summer or -40 F in the winter, whenever possible.