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#4717589 - 04/05/18 07:48 PM Do you think that's "thick" oil? Think again!
Gokhan Online   content

Registered: 12/29/10
Posts: 3115
Loc: Los Angeles, California
Recently there has been concerns regarding premature timing-chair wear, which resulted in people using thicker oils. Many people think that when they use a 0W-40, they are putting in a thick oil because it's "40-grade" when it's at normal operating temperature. It turns out that it's not that simple.

This Nissan study says that timing-chair wear has to do with the base-oil viscosity, not the finished-oil viscosity, which has more to do with the amount of the viscosity-index improver (VII) polymer blended in than the base-oil viscosity. It turns out that for boundary lubrication (metal-to-metal contact), such as in the valvetrain or timing chain, finished viscosity has no effect as the VII molecules are squeezed out and only a microscopic layer of oil is present in addition to the antiwear/extreme pressure/friction modifier (AW/EP/FM) compounds.

Nissan study on wear in timing chains

This brings the question that what's the actual viscosity of the base oil rather than the VII-blended oil, which is an indicator of the oil's ability in protecting boundary- and mixed-lubrication regions (metal-to-metal or partial metal-to-metal contact). Finished, VII-blended viscosity is only an indicator of safeguard against wear in hydrodynamic region, such as the bearings.

The clue on base-oil viscosity comes from the ExxonMobil guide on synthetic-oil blending.

Here are the two rules:

(1) As a general rule, x in xW-y is an excellent indicator of base-oil viscosity. A 5W-20 base oil is a lot thicker than a 0W-20 base oil and a 10W-30 base oil is a lot thicker than a 5W-30 base oil. So, if you really need a thick oil, such as in older engines, in TGDI engines, or any engine where timing-chain or valvetrain wear is a concern, stay of from any 0W-xx or even a 5W-xx oil.

(2) Within the same xW-y group where x is a constant but y varies, such as [0W-20, 0W-30, 0W-40] or [5W-30, 5W-40}, the oil with the smallest spread -- smallest difference between y and x -- has likely the thickest base oil and the oil with the largest spread has likely the thinnest base oil. So, 0W-20 is likely to have a thicker base oil than 0W-40! In fact in my UOA comparison of 0W-20 and 0W-40, I did find out that 0W-20 produced less valvetrain wear (less iron [Fe]) than 0W-40!

To summarize the rules for getting a really thick oil: Find the oil with the largest cold number x and the smallest spread between the hot and cold numbers y - x in the SAE viscosity grade xW-y. It's more crucial for the x to be large than the y - x to be small. A 0W-40 is an awful choice for valvetrain and timing-chain wear protection, as it has the smallest x and largest y - x. 15W-40 would be an excellent choice for a thick oil, because it has a very high cold-viscosity number and a relatively small spread between hot and cold viscosities, which indicates that it actually does have a thick base oil instead of having been thickened by the VII.

Here are the examples given by ExxonMobil. Base-stock viscosities are implied in the names of the base stocks. For example 4 means 4 cSt and 45 means 4.5 cSt. These are the base-oil viscosities calculated from the base stocks and their percentages in the table (4.1 cSt, 5.8 cSt, 8.0 cSt, and 4.3 cSt base stocks, respectively):

SAE grade  Base-oil viscosity at 100 C (KV100 for the base oil)

 0W-20     5.43 cSt
 0W-30     5.16 cSt
 0W-40     5.00 cSt
 5W-30     6.80 cSt
 5W-40     6.56 cSt
 5W-50     6.67 cSt
10W-60     7.90 cSt

So, 0W-40 is the thinnest oil in terms of the base-oil viscosity!

A final note: While x in xW-y is always a good indicator of the actual base-oil viscosity, there are variations in how much the y - x spread affects the base-oil viscosity. While ExxonMobil guide indicates the conclusions here, there are other formulations possible. You are always safe with a large x if you want a thick base oil. However, you will usually have an additional assurance on base-oil thickness if you also choose a small y - x.

1985 Toyota Corolla LE, 4A-LC engine, ~ 270,000 M
Toyota (TGMO) 0W-20 SN synthetic
Mobil 1 EP M1-103 filter, 90430-12031 drain gasket

#4717600 - 04/05/18 07:57 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
SOHCman Offline

Registered: 03/29/10
Posts: 1336
Loc: USA
This is a interesting "study" but at what point can we accept it as truth or proof?
I urge people not to wait 100K to change out the fluid in their transfer case units. -Kestas

#4717610 - 04/05/18 08:02 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
SubieRubyRoo Online   content

Registered: 05/14/12
Posts: 1236
Loc: Winchester, Indiana
So somebody needs to start making a 10W20 oil (or even 15W20), or do we just all start running monogrades again?

#4717614 - 04/05/18 08:05 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
hatt Offline

Registered: 01/03/12
Posts: 4431
Loc: Florida
Looks like I was ahead of the game with my 10w-30 and 15w-30 usage.
2013 F150 5.0, PUP 10W-30, Wix 57502
2010 Camry 2.5, GTX 5W-20, Fram Ultra XG9972

#4717664 - 04/05/18 08:44 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
rooflessVW Online   content

Registered: 12/24/11
Posts: 4349
Loc: North Carolina
This is exactly why I'm considering 15W-40 over 5W-40 for my next change.
"Zed's dead baby, Zed's dead."

#4717667 - 04/05/18 08:47 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
aquariuscsm Offline

Registered: 12/30/06
Posts: 18309
Loc: Dallas,Tx USA
1996 Nissan 300ZX 5-speed,Arctic Pearl(#175 of 300)
Quaker State Ultimate Durability 10W30
2012 Honda Accord Coupe EX-L 2.4,auto,San Marino Red
Quaker State Ultimate Durability 5W30

#4717683 - 04/05/18 08:57 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
Linctex Offline

Registered: 12/31/16
Posts: 6186
Loc: Waco, TX
Yep, straight 30W Oil often delivers outstanding used oil analysis on this form.

Modern straight-grade oils often exhibit much better cold flow characteristics than their compadres from decades ago.

When you look at the numbers, some straight 30W oils are ACTUALLY 15W-30 or 20W-30 oil,
Even though it is labeled as a straight 30 anyway.
"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

#4717698 - 04/05/18 09:04 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
demarpaint Offline

Registered: 07/03/05
Posts: 30030
Loc: NY
I'll stick with 5W30.
God Bless Our Troops

#4717699 - 04/05/18 09:07 PM Re: Do you think that's "thick" oil? Think again! [Re: Linctex]
bbhero Offline

Registered: 03/20/15
Posts: 4746
Loc: Virginia
Really a great point Linctex. The current 30 grade oils really are much better than past ones from years ago. I bet you are right that they really are 15w30 at the end of the day.
Nissan Altima 3.5 Coupe Formula Shell 5w30 Champion 7317
"Treat your family like your friends and treat your friends like your family."

#4717704 - 04/05/18 09:11 PM Re: Do you think that's "thick" oil? Think again! [Re: aquariuscsm]
SubieRubyRoo Online   content

Registered: 05/14/12
Posts: 1236
Loc: Winchester, Indiana
Originally Posted By: aquariuscsm

I was interested... until I saw a 108 VI, 10% NOACK, and a 62.3 viscosity at 100*F. That, and only an API SF rating. Oh well.

#4717708 - 04/05/18 09:17 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
Carbon12 Offline

Registered: 03/10/15
Posts: 199
Loc: MO
Thanks for posting. Counter intuitive but makes a lot of sense after thinking about it. Also thought it was interesting the study confirmed the anti-wear properties of MoDTC which I think this is the first time I seen anything other than just speculation regarding its anti wear properties.

#4717710 - 04/05/18 09:19 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
PeterPolyol Offline

Registered: 03/06/16
Posts: 1351
Loc: toronto
Yes, that's what I'm talkin' about. Nice find Gokh's
It's always reasonable to assume that a benefit in one parameter might come at a cost in another parameter, even if one doesn't know what the catch is yet. Chasing inappropriately low W ratings on high-VI oils, this study would suggest, may unnecessarily increase actual component wear. Love those straight blends thumbsup

#4717711 - 04/05/18 09:22 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
JAG Offline

Registered: 10/23/05
Posts: 4893
Loc: Fredericksburg, VA
Thanks Gokhan. As you know, the “Harman Index” is a great way to quantify how close to Newtonian oils indication of how much VII is used.

The downside is that it requires density, which some data sheets don’t provide. If it doesn’t, another good metric is ratio of HTHS to KV100. Multiply by 10 if you prefer numbers over 1 for readability reasons. It is not as good of a metric because oils of very low or high density get skewed values because kinematic viscosity is itself skewed by density. Dynamic viscosity is the “real” viscosity at low shear rates, while kinematic viscosity is not.

#4717715 - 04/05/18 09:26 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
dave1251 Offline

Registered: 07/15/05
Posts: 8698
Loc: Maricopa, AZ
I will continue to use 5W/10W30's.
make the inside of your engine oil cap white.
don't use.

#4717718 - 04/05/18 09:29 PM Re: Do you think that's "thick" oil? Think again! [Re: Gokhan]
Marco620 Offline

Registered: 02/25/14
Posts: 2220
Loc: Kansan,Heckler Koch fan
So, Im doing right by running 0w20 in my Honda? Good I got like 100 qts of PUP.
2015 Civic 170k mi.0w20 Redline/Archoil,HPS SRI,Yokohama/Borla Exhaust/Vibrant Resonators #1790/Tein Suspension
Go Nashville Predators!

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