Does thicker oil=better protection?

[mechtech2]

Doug Hillary -
Concerning the original Minis:
If the components survived very well on 20 oil, then why go massively thicker to a 50?
The answer is that they did not survive well without it.
Shared gearboxes with engine sumps are rare in cars, but not with motorcycles.

 

[Doug Hillary]

Hi,
mechtech2 - As mentioned earlier - permanent shear was the main culprit

Others were the mix of wear metals (brass etc) and the location and type of seals and sealants. Development commenced in England in the mid 1950s amid an Auto Industry riddled with Industrial disruption and Worker weariness after WW2

Some early delivery cars were also run without sufficient lubricant as they leaked and used so much. As I recall the capacity was increased too (recalibrated dipstick) as a result

You could almost hear the cars leaking 10w30 on a warm still evening!

 

[aquariuscsm]

Which of these 30 weight oils is the "best",in everyone`s opinion:

Mobil 1 10W30HM
Valvoline Synpower 10W30
Valvoline Maxlife 10W30

I`m dropping back down at least to a 40 weight next oil change (in 40 weight I`d go with either M1 10W40HM,Valvoline Maxlife 10W40,Valvoline wb 10W40,or GTX 10W40). The 15W50 seems to take a tiny bit of power from my car. 10W40 seemed perfect! Wonder if 10W30 will be better,without compromising any protection?

 

[HTSS_TR]

Why not try M1 0W40 ? It's thinner than Mobil 1 10W30 HM at cold start but thicker at operating temperature.

 

[Doug Hillary]

Hi,
aquariuscsm - I agree M1 0w-40 would be a good choice. It's recommended by Mobil in OZ for this application

 

[Geonerd]

Originally Posted By: volk06
Wouldn't you want a oil with a higher HTHS for a mod engine that is pushing out a significant amount of more power?


YES!

The Stribeck curve is real! Increased bearing loads strongly suggest an increase in HTHS to maintain the 'standard' oil film thickness.

 

[Shannow]

Agreed...
if the bearing is experiencing increased loads at the same RPM, to maintain the designed in level of protection, i.e. "film thickness" the operating viscosity must be higher.

And as Doug alluded to, account for what else is likely to happen during he OCI...
* permanent shearing;
* dilution;
* oil loss leading to higher oil temps;
* momentary/short term thermal anomolies, like he long big hill etc.

A lot of these threads understate the "thick as necessary", at the very point in time that it really is, actually necessary, versus the "thousands of vehicles that don't have a problem most of the time."

 

[CATERHAM]

Originally Posted By: supercity
What about for a modified engine? Is thicker oil required?
Say engine X is a 2L, 4 cylinder, turbocharged and makes 250hp. With more boost and or rpm it now makes 350hp. Would a higher grade be benificial?

Originally Posted By: dave1251
It may be. But what are oil temps and pressure reading after the modifications vs before?

That's the point. If you're going to start modifying an engine you'd be wise to become very familiar with your oil pressure and oil temp' characteristics of your engine, both before and after the modification unless someone else has has already done he ground work for you.
Yes the minimum viscosity demands of the engine have increased but you don't know if the viscosity reserves of the original spec' oil don't already more than cover it. If for the sake of argument the spec' oil pressure was 60 psi at elevated rev's you could increase that to say 65 psi or even 70 psi if you're really conservative. That will represent an increase in operational viscosity or the minimum viscosity you've willing to accept.
In all likelyhood you're not likely seeing OP less than 70 psi so if that's the case a heavier oil is not required.
But if you're seeing much higher oil temp's then your OP could drop below the level of your determined optimum minimum operational viscosity and then an oil with a somewhat higher HTHSV rating could be required.

Just as a point of interest, Porsche spec's the same 0W-40 oil for all it's engines including the 550 hp twin turbo although the Turbo will see much higher oil temp's than the NA Cayman or Boxster.
BMW spec's the same 5w30 oil for it's twin turbo engine as it does for it's NA non M series engines although it sees much higher oil temp's.
The point is, one shouldn't automatically assume a heavier oil grade will be actually be necessary.
BMW sp

 

[JGW]

Is there a relationship between HTHS values and engine wear?

 

[CATERHAM]

Originally Posted By: JGW
Is there a relationship between HTHS values and engine wear?

Put simply HTHS viscosity is simply an accurate measure of how thick or thin an oil is in an operating IC engine.
Depending on the engine a HTHSV of 3.5cP or so is about the minimum viscosity under high load and still avoid bearing wiping.
But don't confuse that with the HTHSV rating of an oil which is measured at 150C.
For example, the 0W-5 qualifying oil used in some racing series may have a HTHSV as low as 1.7cP, but can run flat out for a few laps with no chance of engine wear as long as the driver lifts before the oil temp's rise above a certain predetermined level; nominally 180F.

 

[edhackett]

Yes. That's why the API sets minimum values for HTHS; 2.6 for gasoline engines and 3.5 for diesels, which have higher cylinder pressures and corresponding bearing loads.

Ed

 

[edhackett]

Also don't confuse the 150C test temperature for HTHS with sump temperature. The higher test temperature is within the normal range seen in the bearing due to local heating due to friction.

Ed

 

[CATERHAM]

To give you a rough idea in most applications a virgin HTHSV 3.5cP oil can withstand sump oil temp's of 145-150C before the onset of bearing wiping under maximum load.
A HTHSV 3.1cP oil may be able to withstand sump oil temp's of 130-135C and a 2.6cP oil temp's of about 120C under the same condtions.

Honda and Toyota have developed 0W-15 (HTHSV 2.3cP) and 0W-10 (HTHSV 2.0cP) oil grades and are using them in Japan. They are in the process of getting these oil grades certified so that they can be used as service fill in export countries. In fact the 0W-10 is the factory fill on some Japanese models like the Honda Insight that we get here. The main reason these light oils can be used successfully is that the maximum sump oil temp's are well contained.

 

[mechanicx]

Originally Posted By: Shannow
Agreed...
if the bearing is experiencing increased loads at the same RPM, to maintain the designed in level of protection, i.e. "film thickness" the operating viscosity must be higher.

And as Doug alluded to, account for what else is likely to happen during he OCI...
* permanent shearing;
* dilution;
* oil loss leading to higher oil temps;
* momentary/short term thermal anomolies, like he long big hill etc.

A lot of these threads understate the "thick as necessary", at the very point in time that it really is, actually necessary, versus the "thousands of vehicles that don't have a problem most of the time."



I will agree somewhat with you there. A thicker oil may not reduce wear but it gives you an added insurance envelope. One should never go thinner than the recommended grade in the US as they have pushed it close to "as thin as possible". And if you modify the engine or operate it outside of the intended perimeters the recommendation goes out the window and going up a grade or even two and/or switching to synthetic may be needed for lower wear and even engine survival. Connecting rod bearings can let go when you push the oil too far.

 

[Ken2]

The design of the engine is another critical factor. A larger bearing surface with the same load will have fewer pounds per square inch of force on the oil film, so a lighter viscosity can be used, and vice versa. Other things remaining equal, higher viscosity gives a higher film strength. But, how much is enough? As an example, the crankcase in a very large diesel engine putting 7,500 hp into each con rod bearing uses 30 wt oil. It is all engineered as a package. The 6' diameter turbochargers for this engine will use an ISO64 turbine oil, about a 20 wt or light 30 wt. Again, engineered as a package.

 

[Jim Allen]

Originally Posted By: CATERHAM
To give you a rough idea in most applications a virgin HTHSV 3.5cP oil can withstand sump oil temp's of 145-150C before the onset of bearing wiping under maximum load.
A HTHSV 3.1cP oil may be able to withstand sump oil temp's of 130-135C and a 2.6cP oil temp's of about 120C under the same conditions.


Very interesting and potentially useful info for me. I don't know if I've seen you quote these number before. If you did, I must really be slipping as I actively look for the closest thing I can find to generalities that fit the broadest possible application. From whence did this info come? A fellow oil temp watcher wants to know ( : < )!

A great discussion here, folks, with all sides covered and highlighting the fact that one size does NOT fit all. A fair bit of specific knowledge is needed to tailer the oil to applications that may fall outside the envelope the engineers envisioned.

As the weather here has warmed up, I find my new (ish) bypass filter is having a cooling effect on the oil in the neighborhood of 10-20 degrees (I'll get that narrowed down a bit). I may be too far outside the "as thick as necessary" for this application now (I'm running a 10W30 HDEO fleet oil in a 5.4L Ford designed for 5W20.

 

[Geonerd]

Originally Posted By: Ken2
The design of the engine is another critical factor. A larger bearing surface with the same load will have fewer pounds per square inch of force on the oil film, so a lighter viscosity can be used, and vice versa. Other things remaining equal, higher viscosity gives a higher film strength. But, how much is enough? As an example, the crankcase in a very large diesel engine putting 7,500 hp into each con rod bearing uses 30 wt oil. It is all engineered as a package. The 6' diameter turbochargers for this engine will use an ISO64 turbine oil, about a 20 wt or light 30 wt. Again, engineered as a package.


Indeed!

This is why dumping xW-20 in a high output sportscar that specifies xW-50/60 is pure folly.

And just because you can tootle your xW-20 filled Ferrari to the store and back for a loaf of bread w/o lunching the engine does not imply that your oil of choice is remotely appropriate. IMO, unless you happen to design engines in Maranello, you have no business second-guessing the owner's manual.

 

[CATERHAM]

Originally Posted By: Geonerd
Originally Posted By: Ken2

This is why dumping xW-20 in a high output sportscar that specifies xW-50/60 is pure folly.
And just because you can tootle your xW-20 filled Ferrari to the store and back for a loaf of bread w/o lunching the engine does not imply that your oil of choice is remotely appropriate.

That's exactly what it means. If you drive the car like your grandmother drives her Prius the oil choice should be the same. A 10W-60 is what's not appropriate.
BTW, I don't know anyone including our Enso owning A.E. Haas who has ever run a 20wt oil in his Ferrari.
Fortunately Ferrari doesn't spec' anything heavier than a 3.6cP 5W-40 for it's current range of models.

 

[CATERHAM]

Originally Posted By: Geonerd
Originally Posted By: Ken2

This is why dumping xW-20 in a high output sportscar that specifies xW-50/60 is pure folly.
And just because you can tootle your xW-20 filled Ferrari to the store and back for a loaf of bread w/o lunching the engine does not imply that your oil of choice is remotely appropriate.

That's exactly what it means. If you drive the car like your grandmother drives her Prius the oil choice should be the same. A 10W-60 is what's not appropriate.
BTW, I don't know anyone including our Enso owning A.E. Haas who has ever run a 20wt oil in his Ferrari.
Fortunately Ferrari doesn't spec' anything heavier than a 3.6cP 5W-40 for it's current range of models.

 

[fdcg27]

Originally Posted By: aquariuscsm
Which of these 30 weight oils is the "best",in everyone`s opinion:

Mobil 1 10W30HM
Valvoline Synpower 10W30
Valvoline Maxlife 10W30

I`m dropping back down at least to a 40 weight next oil change (in 40 weight I`d go with either M1 10W40HM,Valvoline Maxlife 10W40,Valvoline wb 10W40,or GTX 10W40). The 15W50 seems to take a tiny bit of power from my car. 10W40 seemed perfect! Wonder if 10W30 will be better,without compromising any protection?


Best for what?
The M1 HM is a higher HTHS oil than are the two Valvoline oils.
The M1 will permit longer drains than either Synpower or Maxlife.
I didn't check, but the Maxlife is probably thicker than the Synpower.
If you don't intend to run long drains, I'd try the Maxlife, although I might use the 10W-40.