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#2125973 - 01/03/11 05:05 PM If synthetic 5w40 protects hot like it should
Ponch Offline


Registered: 01/12/08
Posts: 263
Loc: Bay City Michigan
...then why the lower HT/HS numbers? I notice some oil companies who publish these HT/HS specs on HDEO dino 15w40, but when you look at that same companies specs on their synthetic 5w40 oil...they do not post that info/spec. The companies that did indeed post the HT/HS specs for 15w40 and 5w40, their "synthetic" HT/HS number is lower then it's dino 15w40 counterpart. Hence the reasoning I am sticking with 15w40 dino oil in summer, and 5w40 in winter in my duramax. I am NOT taking a chance on a very expensive engine running a 5w40 in summer while towing. Some of you may agree with me, and some not....this is what makes me feel better. I have read online that duramax oil temps can get severely high while towing, and if i understand correctly, as your oil temp rises your oil thins out more and more, so I would rather "thin out" a stout 15w40, rather than a 5w40, or a 10w30. I am not brave enough as "dnewton3" or "arkapig" to run a 10w30 in my duramax yet.....

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#2125980 - 01/03/11 05:12 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
Panzerman Offline


Registered: 12/16/06
Posts: 2482
Loc: Daytona, Florida
I would think a 5w40 would be fine versus a 15w40. Its the 40 number you are looking at. 5w40 would just give you some colder, easier starting. 5w40 would exceed the 15w40 specs. I dont think I would go with the 10w30 though. I am not a big believer in 5w20 in gasoline trucks used for towing either. I have seen what heat does to oil and its not pretty. Either way 15w40 would be fine year around in about any vehicle, gas or diesel. Contrary to popular belief, 15w40 doesnt freeze solid at 32 degrees like some seem to think.


Edited by Panzerman (01/03/11 05:14 PM)

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#2126025 - 01/03/11 05:44 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
CATERHAM Online   content


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
You are correct, the HTHS vis is the spec' to look at to judge how thick or thin any oil is at operating temps.
Having said that, even in high oil temp' situations you rarely need an oil with a HTHS vis' greater than 3.8cP unless the engine already has loose bearings.

But instead of guessing on what your engine may need in towing situations in the summer, install an oil pressure gauge. If you do, I think you'll pleasantly surprised to learn that you very likely don't actually need anything heavier than a 30wt oil.
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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#2126067 - 01/03/11 06:18 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
dparm Offline


Registered: 04/19/10
Posts: 12503
Loc: Chicago, IL
There are plenty of 5w40s with HTHS above 4.0. In fact, Motul 300V 5w40 has an HTHS of 4.51.

The VW/Audi-specific Castrol SLX 5w40 oils are all 3.5 or greater. Not sure of their exact values.
_________________________
2011.5 BMW M3 saloon ZCP
der stärkste buchstabe der welt
Castrol Edge Professional TWS 10w60 + Mahle OX 254D3

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#2126086 - 01/03/11 06:35 PM Re: If synthetic 5w40 protects hot like it should [Re: CATERHAM]
daman Offline


Registered: 09/23/06
Posts: 10480
Loc: Bad Axe, MI
Originally Posted By: CATERHAM
You are correct, the HTHS vis is the spec' to look at to judge how thick or thin any oil is at operating temps.
Having said that, even in high oil temp' situations you rarely need an oil with a HTHS vis' greater than 3.8cP unless the engine already has loose bearings.

But instead of guessing on what your engine may need in towing situations in the summer, install an oil pressure gauge. If you do, I think you'll pleasantly surprised to learn that you very likely don't actually need anything heavier than a 30wt oil.

Correct if oil pressure is sufficient to engine manufactures specs your good.
_________________________
"Always"....Mobil 1

Current fill: AFE 0w30

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#2126201 - 01/03/11 08:15 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
unixguru Offline


Registered: 06/24/10
Posts: 227
Loc: CA
I don't think that would be an issue to use 5w40 instead of 15w40 in the summer. Though I agree with you that 15w40 might have a higher HTHS number than synthetic 5w40, I would think that synthetic 5w40 will keep its HTHS number better in high temperature conditions than mineral oil.

Just a theoretical example (not the actual numbers):

OIL TEMP(degrees C) 100 120C 140C
HTHS 15w40 mineral: 4.5 4.1 3.7
HTHS 5w40 synthetic: 3.9 3.6 3.3

I would think that as temperature increases, good synthetic formulation would retain HTHS number better. Besides you also have to consider temporary as well as permanent oil shearing. Mineral oil would shear much, much faster compared to synthetic and lose originally rated HTHS number while synthetic might keep its rated HTHS number very close to new oil rating.

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#2126242 - 01/03/11 08:59 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
Doug Hillary Online   content


Registered: 05/30/03
Posts: 4837
Loc: Airlie Beach Australia
Hi,
Ponch - Most significant NA diesel engine Manufacturers had/have a minimum HTHS viscosity of 3.7cP

I used 5W-40 HDEOs in my Detroit Series 60s for millions of kms in temperatures up to 50C - this is at a GTM of 42t (around 93000lbs). Much of their work was done with temperature variations from -10C to 50C - this work included long periods of WOT (almost) (for Aussies - on the Newell Hiway). My maximum oil temperature was 112C and the Fleet opersting average was 103C. These engines allow up to 115C before a warning is given with power down (to stop) at 121C. Up to 110C is considered normal

My engine showed exceptionally low wear characteristics at teardown inspection at 1.2m kms

Not all 5W-40s are HDEOs and it does pay to read the Spec sheets
_________________________
Regards
Doug

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#2126405 - 01/03/11 11:21 PM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
Ken2 Offline


Registered: 12/02/02
Posts: 6150
Loc: Washington St.
5W-40 HTHS vis can be as low as 2.9 according to the SAE J300 spec. 15W-40 must be no lower than 3.7. The lower vis will be mainly gasoline engine 5W-40, while the oil companies will make their HDEO 5W-40 3.7 or higher...check with the oil company's web site or email them. The 5W-40 I use is 4.5.
_________________________
Every gun that is made, every warship launched..a theft from those who hunger and are not fed, those who are cold and not clothed.
Gen. Eisenhower


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#2126477 - 01/04/11 02:24 AM Re: If synthetic 5w40 protects hot like it should [Re: unixguru]
CATERHAM Online   content


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Originally Posted By: unixguru
I don't think that would be an issue to use 5w40 instead of 15w40 in the summer. Though I agree with you that 15w40 might have a higher HTHS number than synthetic 5w40, I would think that synthetic 5w40 will keep its HTHS number better in high temperature conditions than mineral oil.

Just a theoretical example (not the actual numbers):

OIL TEMP(degrees C) 100 120C 140C
HTHS 15w40 mineral: 4.5 4.1 3.7
HTHS 5w40 synthetic: 3.9 3.6 3.3

I would think that as temperature increases, good synthetic formulation would retain HTHS number better. Besides you also have to consider temporary as well as permanent oil shearing. Mineral oil would shear much, much faster compared to synthetic and lose originally rated HTHS number while synthetic might keep its rated HTHS number very close to new oil rating.

Not sure what you're trying to say but HTHS vis is of course measured at 150C.
Oil shear is largely a result of a high VII content in an oil.
Shear is not a problem per se as long as you familiar with the oil you dealing with. Just one more reason why an oil pressure gauge is so useful in high stress situations to monitor what's going on with your oil.
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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#2126602 - 01/04/11 08:21 AM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
BoiseRob Offline


Registered: 12/09/06
Posts: 233
Loc: Idaho
Originally Posted By: Ponch
...then why the lower HT/HS numbers? I notice some oil companies who publish these HT/HS specs on HDEO dino 15w40, but when you look at that same companies specs on their synthetic 5w40 oil...they do not post that info/spec. The companies that did indeed post the HT/HS specs for 15w40 and 5w40, their "synthetic" HT/HS number is lower then it's dino 15w40 counterpart. Hence the reasoning I am sticking with 15w40 dino oil in summer, and 5w40 in winter in my duramax. I am NOT taking a chance on a very expensive engine running a 5w40 in summer while towing. Some of you may agree with me, and some not....this is what makes me feel better. I have read online that duramax oil temps can get severely high while towing, and if i understand correctly, as your oil temp rises your oil thins out more and more, so I would rather "thin out" a stout 15w40, rather than a 5w40, or a 10w30. I am not brave enough as "dnewton3" or "arkapig" to run a 10w30 in my duramax yet.....


Ponch,

Schaeffer's Supreme 9000 5w40 has a higher HTHS number than their Supreme 7000 15w40.

Supreme 9000 5w40 HTHS = 4.5
Supreme 7000 15w40 HTHS = 4.3

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#2126645 - 01/04/11 09:15 AM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
A_Harman Offline


Registered: 10/01/10
Posts: 4179
Loc: Michigan
Hi Ponch,

I went through the same thought process when I was looking to switch my 2001 Dodge/Cummins over from the 15W-40 Valvoline Premium Blue Classic to some 5W-40 synthetic. The spec sheet for PB Classic showed HTHS vis of 4.2, and it was difficult to find a 5W-40 that was equivalent. It seems like the problem in formulating a 5w-40 oil is that a lot of VI Improver must be added to get the wide viscosity range, and large amounts of VII lead to low HTHS viscosity.

The HTHS of some 5w-40 diesel oils:
VPB Extreme = 3.8
M1 TDT = 3.8
AMSOil = 4.0
Redline = 4.6
Shell Rotella T6 = not listed

The spec for Redline 5W-40 just knocks me out. Maybe it's due to their predominantly POE base stock? If cost and availability are not issues with you, I would recommend that you consider Redline. In the end, I went with M1 TDT because of its lower cost and ready availability.
_________________________
1985 Z51 Corvette track car
2002 Camaro Z28 LS1/6-speed
2001 Dodge Ram 2500 diesel
1972 GMC 1500 shortbed project truck

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#2126657 - 01/04/11 09:32 AM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
m37charlie Offline


Registered: 06/08/09
Posts: 1127
Loc: Alaska
This is older data from 10 yrs ago, when CH4 Delvac 1 5W40 was being formulated:
HTHS = 4.1
HTHS after ASTM 6278 shearing = 4.1
Although the additives have changed, i doubt the base oil has changed much.
"Performance of an Advanced Synthetic Diesel Engine Oil", SAE paper 2000-01-1993

Charlie
_________________________
05 Unimog U500/Unicat camper/Delvac 1 SHC ACEA E4/E5
09 BMW X5 35d/Delvac1 LE 5W30
01 BMW 325xi M1 0W40
52 Dodge M37/Hercules diesel
79 BJ40 Landcruiser

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#2126856 - 01/04/11 11:52 AM Re: If synthetic 5w40 protects hot like it should [Re: Ponch]
CATERHAM Online   content


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
Originally Posted By: A_Harman
Hi Ponch,

I went through the same thought process when I was looking to switch my 2001 Dodge/Cummins over from the 15W-40 Valvoline Premium Blue Classic to some 5W-40 synthetic. The spec sheet for PB Classic showed HTHS vis of 4.2, and it was difficult to find a 5W-40 that was equivalent. It seems like the problem in formulating a 5w-40 oil is that a lot of VI Improver must be added to get the wide viscosity range, and large amounts of VII lead to low HTHS viscosity.

The HTHS of some 5w-40 diesel oils:
VPB Extreme = 3.8
M1 TDT = 3.8
AMSOil = 4.0
Redline = 4.6
Shell Rotella T6 = not listed

The spec for Redline 5W-40 just knocks me out. Maybe it's due to their predominantly POE base stock? If cost and availability are not issues with you, I would recommend that you consider Redline. In the end, I went with M1 TDT because of its lower cost and ready availability.


Red Line generally recommends dropping a grade when switching to their 5W-XX oils and for good reason.
If you want a so-called 40wt oil with an unprecidently high HTHS vis' you could consider RLI's 15W-40 at 5.21cP although I wouldn't recommend it.
These RLI and RL oils are really 50wt oils since the HTHS vis' spec' trumps the KV100 spec'.

It is a myth that you'll garner better engine protection at high operating temp's by choosing the highest HTHS vis for a given SAE grade. All you're doing is selecting a thicker oil at ALL normal operating temp's. The objective should be to select an oil with a
HTHS vis' that meets your needs. Anything higher than that is counter productive to what you're trying to achieve; namely long engine life.
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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#2127183 - 01/04/11 03:54 PM Re: If synthetic 5w40 protects hot like it should [Re: CATERHAM]
A_Harman Offline


Registered: 10/01/10
Posts: 4179
Loc: Michigan
Originally Posted By: CATERHAM

It is a myth that you'll garner better engine protection at high operating temp's by choosing the highest HTHS vis for a given SAE grade. All you're doing is selecting a thicker oil at ALL normal operating temp's. The objective should be to select an oil with a
HTHS vis' that meets your needs. Anything higher than that is counter productive to what you're trying to achieve; namely long engine life.


This is the first thing I have read in any of your posts that I disagree with. I think the HTHS test was created to provide a comparison under high stress conditions between oils that have nominally the same kinematic viscosities. Here are viscosity numbers from a couple of the oils we were discussing:

For M1 TDT: KV40=97.9, KV100=14.5, HTHS=3.8
For RL 5w40: KV40=94, KV100=15.1, HTHS=4.6

The kinematic viscosity numbers are within 4% between M1 and RL, yet the HTHS viscosity is 20% higher for RL. (The 40C viscosity for Redline is actually lower than the M1.) In general, when calculating oil film thicknesses in a hydrodynamic bearing, higher viscosity means higher oil film thickness, and better protection for your engine from the standpoint of keeping moving surfaces separated.

Actually determining what minimum HTHS viscosity is required for an engine requires more detailed information than is available to anyone outside of an engineer working for an OEM analyzing a specific engine. This engineer would require knowledge of maximum allowable bearing clearance, bearing diameter, crankshaft speed, and bearing radial loads to be able to calculate the minimum oil film thickness. Then he would compare this result to surface finish values for the bearing and crank to evaluate if the surfaces remain purely in hydrodynamic lubrication, or if they fall into boundary lubrication, and would be subject to much higher wear.
_________________________
1985 Z51 Corvette track car
2002 Camaro Z28 LS1/6-speed
2001 Dodge Ram 2500 diesel
1972 GMC 1500 shortbed project truck

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#2127269 - 01/04/11 04:55 PM Re: If synthetic 5w40 protects hot like it should [Re: A_Harman]
CATERHAM Online   content


Registered: 11/18/05
Posts: 9448
Loc: Burlington, Ontario, Canada
HTHS viscosity is what you say it is but what I find from a practical view point that is most important is that it is a measure of viscosity that closely replicates the actual operational viscosity in an engine under stress (pressure).
The very simple kinematic method of measuring viscosity does not correlate well with the operational viscosity in an engine as determined by oil pressure.
The net effect of this is that oil's with the same HTHS viscosity will have the same operational viscosity at normal operating oil temp's and above REGARDLESS of what their KV100 spec's might be.
The following link explains in further detail:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2004057&page=1
_________________________
74 Lotus Europa 5W-50
86 Porsche 928S TGMO 0W-20 25%/M1 0W-40
96 BMW 328i Idemitsu/TGMO 0W-20 70%/M1 0W-40
94 Caterham 7 Sustina 0W-20 80%/0W-50

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