Mobil 1 15w-50 film strength

[Threeofnine]

I have a 1988 Ferrari Testarossa and a 1985 Ferrari Mondial. Both cars have flat tappet engines. I’ve been using Mobil 1 15w50 in both cars (factory recommendation is a 10w50 oil). I always figured 15w50 would be a very stout oil but I ran across a thread (linked below) that appears to show it has mediocre film strength. In fact, if I’m reading, right Mobil 1 5w30 has a significantly higher film strength. This makes me a little concerned as both cars are typically driven fast, often well into the triple digits, and the RPMs get pretty high. Should I be concerned or is there more to it?

D

Thread 'Capacity / Film Strength Oil Test 48 Oils.'

Oct 21, 2013

C/P From 540 RAT
From another Forum

If this is already here, then sorry. However I found this to be very very interesting



READ THIS ALL, I WAS SHOCKED TO SEE REGULAR CHEVERON 5W30s capacity/film strength” compared to other oils that cost 2X or even 3X more.


Quake State Defy and High Zinc Oils, How much Zinc and how they perform where it counts in real world tests Capacity / Film Strength Test

This synthetic blend motor oil costs $5.29 per quart at Pep Boys. So, it is roughly half the price of a name brand, top of the line, full synthetic motor oil.

Some...

• David1
• Replies: 18
• Forum: Passenger Car Motor Oil (PCMO) - Gasoline Vehicles

 

[kschachn]

We need another one of these threads?

Did you read all of that thread and any substantive comments? What about the 20 other long threads on this topic?

 

[JavierH19]

That is a 540 rat "test" it's based on nothing more than smoke inhaled from a black residue tainted glass pipe.

 

[RooflessVW]

You can safely disregard any information associated with "540 RAT"

 

[JavierH19]

I still have no clue how he got those psi numbers. What testing methodology even is that.

 

[kschachn]

I still have no clue how he got those psi numbers. What testing methodology even is that.

When you consider it all it’s the definition of a dumpster fire.

 

[dnewton3]

I would put zero stock in the "tests" and results of that old Rat540 thread.

 

[Glenda W.]

I still have no clue how he got those psi numbers. What testing methodology even is that.

It’s top secret….

 

[MolaKule]

It seems the definition of film strength has eluded many, including RAT540:

"Film Strength​

Film strength can be described as the lubricant’s ability to lessen the effects of friction and control wear by means other than the film thickness. As mentioned, the viscosity is the primary contributor to film thickness during hydrodynamic and elastohydrodynamic lubrication.

When the base oil viscosity is insufficient to overcome metal-to-metal surface contact, the base oil and additive chemistry work together to create a surface protection mechanism. During these boundary conditions, boundary lubrication is also influenced by the chemical and physical properties of the mechanical surfaces and any contributing environmental factors.

Even when loads and temperatures are higher and relative surface velocities are lower, the film strength is improved..."

https://www.machinerylubrication.com/Read/30835/lubricant-film-strength

 

[SR5]

Ignore the 540RAT claims. Keep using M1 15W50, it's a great oil for your application.

 

[userfriendly]

I read somewhere that “Under stress a lubricant is reduced to its base oil viscosity.”

That would be different from temporary shear of polymer additives in the bearing clearances from rotational forces.

I believe the statement indicated that temporary shear can also be caused by high load pressure between surfaces separated by an oil film.

If so, the viscosity of an engine oil containing VII polymer additives will be reduced providing the oil was at a temperature high enough to cause the VIIs to thicken the oil.

A loss of viscosity will lower the film strength.

Obviously an engine oil that does not contain polymer viscosity modifier's will not experience viscosity loss from stress.

 

[FowVay]

I think Rat is simply calculating the pressure/viscosity coefficient for the lubricants when they're in the elastohydrodynamic phase of lubrication. Naturally this is completely dependent on the type of lubricant, whether a mineral, PAO, ester, etc., but it gives the ability to state a definite pressure phase for the fluid. The magazine "Machinery Lubrication" published by Noria has a great article titled "Selecting Oils with High Pressure-Viscosity Coefficient" that shows how different base oils perform. It's a very interesting read and I think it's how Mr. Rat is coming up with is ratings.

 

[burbguy82]

Are film strength and HTHS hand in hand?

 

[RDY4WAR]

You can ignore anything posted by 540rat. It's pseudo-science.

The oil used by Sprint engines, turning 9000 rpm with 910+ HP on methanol and 300°F oil temp, performs rather poorly in that test. Think about that for a minute. if you ran Head and Shoulders through his test, it would shoot to the top of the list, but your engine won't last long on shampoo.

Film strength is a gear oil spec, not an engine oil spec. The film strength figures aren't accurate anyway. What he's doing is back-calculating a film strength number from a bearing scar. He might as well be trying to hit a 500 yard target with a blunderbuss

 

[Cujet]

In my experienced opinion, M1 15W-50 is a superb oil for high stress applications. We've used it in turbocharged race cars for many decades. Even with the occasional reformulations, 15W-50 continues to perform where less viscous oils lead to failure.

It is not particularly 'thick' (viscous) for a 15W-50 and markedly less viscous than many 'racing' 20W-50 oils. I think of its viscosity as between a 10W-40 and a racing 20W-50. HTHS is said to be 4.5. A very nice place to be for an oil that may see excessive temperatures and high loads.

 

[4WD]

In my experienced opinion, M1 15W-50 is a superb oil for high stress applications. We've used it in turbocharged race cars for many decades. Even with the occasional reformulations, 15W-50 continues to perform where less viscous oils lead to failure.

It is not particularly 'thick' (viscous) for a 15W-50 and markedly less viscous than many 'racing' 20W-50 oils. I think of its viscosity as between a 10W-40 and a racing 20W-50. HTHS is said to be 4.5. A very nice place to be for an oil that may see excessive temperatures and high loads.

My coworker has a Trinity powered actual Shelby - last year made …
That ‘Snake’ was filled with Mobil 1 15W-50 - he stayed with that …
This is a serious car …

 

[Hohn]

In my experienced opinion, M1 15W-50 is a superb oil for high stress applications. We've used it in turbocharged race cars for many decades. Even with the occasional reformulations, 15W-50 continues to perform where less viscous oils lead to failure.

It is not particularly 'thick' (viscous) for a 15W-50 and markedly less viscous than many 'racing' 20W-50 oils. I think of its viscosity as between a 10W-40 and a racing 20W-50. HTHS is said to be 4.5. A very nice place to be for an oil that may see excessive temperatures and high loads.

M1 15w-50 is IMHO one of the best choices you can make for a hard-use "Wal mart aisle" oil (my local WMT carries it).

The HTHS of 4.5 is sufficient for almost all but the hottest running, highest loaded applications. By comparison, the 5w-50 FS has an HTHS of only 4.3.


My contrast, the HPL 5w-50 Super Car has an HTHS of 4.7, allowing both higher HTHS and with superior cold flow.

Of course, if you really want high HTHS in an oil that can be used on the street in a warm weather car, there's the HPL PCMO 20w-50 with its stratospherically high HTHS. This stuff is a hell-for-leather stout oil. Note that it's still pouring at -56F as a 20w!

Shell shows are recommendation of 5w-40 Ultra Helix for that car, and any of the 50 grade oils above will have significantly higher HTHS than the Shell Helix Ultra in 5w-40. That oil has an HTHS < 4.0 in most sources.

 

[Cujet]

Thread 'Highest HTHS oils available, taking into account shear stability'

Feb 28, 2025

All about the highest HTHS oils available, not concentrating on motorycles oils specifically, however, MC oils do tend to be high up on the list. My experience is very positive with M1's 20W-50 V-Twin oil in turbocharged race cars.

A friend with a KTM recently asked me about the most robust oils available. I suggested M1, V-Twin 20W-50 due to the superb resistance to shear and the high HTHS, which by memory is 5.9, and it is believed to be free of VII's too! Redline 20W-50 Motorcycle oil has a published HTHS of 6.1 along with similarly excellent ZDDP levels (2200/2000). The Redline might...

• Cujet
• Replies: 36
• Forum: Passenger Car Motor Oil (PCMO) - Gasoline Vehicles

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That thread has a short list of high HTHS oils. In our turbocharged road race cars, if we needed more protection than M1 15W-50, we simply stepped up to M1, 20W-50 V-Twin oil, with an HTHS of 5.7 and zero VII's.

 

[userfriendly]

The intent of engine oils like Dexos R 5W50 is to ensure high oil pressure to bearings and rotating parts furthest from the oil pump without causing excessive heat and power loss from redundant HTHS.

 

[TomYoung]

We need another one of these threads?

Did you read all of that thread and any substantive comments? What about the 20 other long threads on this topic?

In his defense, this post starts out with “I have a 1988 Ferrari Testarossa and a 1985 Ferrari Mondial.” That’s what we should be focused on.