mixing oils can eat your engine?

[CATERHAM]

Originally Posted By: OVERKILL
Originally Posted By: CATERHAM
The single most important aspect of an oil is it's viscosity and you can't talk about viscosity without referencing the viscosity index.

VI is not just important in formulating light oils such as the Japanese OEM 0W-20's. Mobil 1 0W-40 is original OEM high VI oil as is the new Pennzoil Ultra 0W-40.
High VI oils are the trend in racing as well.
Both of Mobil's racing oils are high VI; their 0w50 having a 189 VI.The advantages in racing are clear. An oil that doesn't thin out as much at high temperatures is the holy grail while still being relatively light on start-up.




But I'm not talking about racing oils, I'm talking about high performance oils used for drain intervals in cars like Audi's, BMW's, Mercedes....etc. Oils that have to last longer than a few hours in service.

The VI on Mobil 1 0w-40 went DOWN with the SN formulation. Pennzoil Ultra 0w-40 has no OEM approvals other than Chrysler's, you are better to speak of Pennzoil Ultra 5w-40, which has almost an identical approval/certification list to Mobil 1 0w-40.

And one can certainly speak about viscosity without talking about VI. We talk about HTHS on here all the time without referencing an oil's VI.

Mobil 1 0w-40 has a relatively high VI. But isn't lauded for this trait like the 200+ VI OEM 0w-20's that you've spoken about recently, or the ENEOS oils. And when they made the oil more shear stable, the VI went down.
Originally Posted By: OVERKILL
Originally Posted By: CATERHAM
The single most important aspect of an oil is it's viscosity and you can't talk about viscosity without referencing the viscosity index.

VI is not just important in formulating light oils such as the Japanese OEM 0W-20's. Mobil 1 0W-40 is original OEM high VI oil as is the new Pennzoil Ultra 0W-40.
High VI oils are the trend in racing as well.
Both of Mobil's racing oils are high VI; their 0w50 having a 189 VI.The advantages in racing are clear. An oil that doesn't thin out as much at high temperatures is the holy grail while still being relatively light on start-up.




But I'm not talking about racing oils, I'm talking about high performance oils used for drain intervals in cars like Audi's, BMW's, Mercedes....etc. Oils that have to last longer than a few hours in service.

The VI on Mobil 1 0w-40 went DOWN with the SN formulation. Pennzoil Ultra 0w-40 has no OEM approvals other than Chrysler's, you are better to speak of Pennzoil Ultra 5w-40, which has almost an identical approval/certification list to Mobil 1 0w-40.

And one can certainly speak about viscosity without talking about VI. We talk about HTHS on here all the time without referencing an oil's VI.

Mobil 1 0w-40 has a relatively high VI.

Their is nothing tougher on an oil's shear stability than racing
and 24 hours of Le Mans among other long distance races is what Mobil 1 0w50 was developed for.

Kind of silly saying MI 0W-40's VI has dropped from the SM (185-187)to the SN (185).

Yes we often talk about HTHSV without talking about he oils VI but that's because most heavier oils have VIs that fall within a narrow range but is you want to be precise about operational viscosity at normal operating temp's you should reference the oil's VI.
This is much more important with the ultra high 200+ VI oils since a 60-80 point VI difference between oils will the same HTHSV will significantly lower the operational viscosity at normal operating temp's.
This again is just one trait of high VI oils that most don't fully appreciate.

Unless one has a viscometer in their vehicle the full ramifications of VI will not be experienced by most members.

 

[CATERHAM]

Originally Posted By: S65AMG
If a manufacturer recommends a particular brand and type of oil and they also recommend 20 weight below 86f and 30 weight above 86f, there must be a temperature range where a 25 weight in that brand and type would be more optimal than either.

Mixing two recommended oils that are identical apart from weight to produce that 25 weight oil would seem to have no adverse implications and would produce a more optimal viscosity at certain temperature ranges.

S65AMG you make a good point.
Risking being pedantic, SAE grades are ranges of viscosities, so if you mix a 20wt and a 30wt you'll end up with either a heavy 20wt or a light 30wt. Point being that you need to know the underlying viscosity spec's from a formulators PDS to know more precisely what the blend will produce.

 

[OVERKILL]

Originally Posted By: CATERHAM

Their is nothing tougher on an oil's shear stability than racing
and 24 hours of Le Mans among other long distance races is what Mobil 1 0w50 was developed for.


Yet my understanding is that Mobil 1 0w-40 is used extensively in this event.....? Which has a lower VI

LOL! (yes, I'm just bugging you now) Pennzoil Ultra 5w-40 has a significantly lower VI than either of these lubes though, and it is a popular racing oil from what I understand as well.

Quote:
Kind of silly saying MI 0W-40's VI has dropped from the SM (185-187)to the SN (185).


But it DID drop, from 187 to 185, while not a big drop by any stretch of the imagination it was indeed a drop. And coincidentally or not, the SN version is more shear stable than the SM version. And the pour point went up, and the MRV and CCS increased too.

Quote:
Yes we often talk about HTHSV without talking about he oils VI but that's because most heavier oils have VIs that fall within a narrow range but is you want to be precise about operational viscosity at normal operating temp's you should reference the oil's VI.
This is much more important with the ultra high 200+ VI oils since a 60-80 point VI difference between oils will the same HTHSV will significantly lower the operational viscosity at normal operating temp's.
This again is just one trait of high VI oils that most don't fully appreciate.

Unless one has a viscometer in their vehicle the full ramifications of VI will not be experienced by most members.


OK, but most of us aren't using these ultra high (200+) VI oils. And many of our vehicles don't call for such lubes (like all of mine).

And the same goes for many high performance cars like the ones I referenced earlier. None of them call for 0w-20. Most call for a >=3.5cP HTHS euro oil in a 0w-30/5w30/0w-40/5w-40 grade. Of which the VI's are all over the map.

 

[buster]

The ultra high VI oils are more suited for fuel economy and are being used by Japanese OEM's in 4cyl applications.

Take a look at Amsoil Dominator or Redline racing oils and you'll find the VI is very low. It's low because shear stability is more critical.

VI for the Dominator 5w20 and 10w30 is 152 and 155.

High-Temperature/High-Shear Viscosity
150ºC, 1.4 x 106s-1, cP (ASTM D 5481).


High VI is not always ideal in racing. I doubt you'll see a racing oil with a VI over 200.

 

[S65AMG]

And yet Mobil 1 0w40 has a high VI and is used in racing.

 

[Trav]

Overkill stop making sense. It couldn't be that shell has figured out that their superior GTL base stocks don't require as high a VI Could it.
Just like there NOAK could not be 6.6%, no way no how it has to be at least 12%.
So much for that noise.

Originally Posted By: S65AMG
Please be more nuanced and analytical in your reading and responses. That's what optimizing is about.

You know for a newb you get right in there like you have known everyone for years and you probably do, as we know you.
Ok Mori, FoxS, Mark Stark or the name of this week. Will do.

 

[buster]

Originally Posted By: S65AMG
And yet Mobil 1 0w40 has a high VI and is used in racing.


Due to the natural vi from the high quality base oils and esters being used with VII's.

 

[buster]

From Roy Howell a few years back.

Viscosity Index Improvers
Rubber and Plastic Polymers

Start with a base of straight weight Oil. Then add a polymeric thickener. When hot, the long polymer chain is really moving around, causing the oil to flow less. When cold, the polymers stick to each other, essentially comming out of suspension. The polymers are stable up to about 210 F, where they start to break up. The drawbacks to VI polymers is that they can cause engine dirt because of their low shear strength.


What this chart shows is that a straight oil has the same viscosity regardless of shear rate. However, as the shear rate increases, the shear breaks down the VI polymers, and multigrade oils have less actual viscosity at the localized high shear rate area.
The weak link is the rod bearings and Cam, in terms of rate of shear. There is less friction at the piston rings. Anti Wear is much more important at the cam.

 

[Tempest]

Quote:
and multigrade oils have less actual viscosity at the localized high shear rate area.

Which is why I prefer oils with less VII. It's less important in motor oils than in gear oils but it is still relevant.

 

[S65AMG]

Originally Posted By: buster
Originally Posted By: S65AMG
And yet Mobil 1 0w40 has a high VI and is used in racing.


Due to the natural vi from the high quality base oils and esters being used with VII's.


So they decided to add VIIs to high quality base oils. Why would they do that if the competition doesn't and it's the factory fill in AMG vehicles (but not other Mercedes)?

 

[Tempest]

Originally Posted By: CATERHAM
The single most important aspect of an oil is it's viscosity and you can't talk about viscosity without referencing the viscosity index.

A few years ago, member Gary Allan ran some custom made 0W10/20 (depending on how one looked at it) in a car that spec'ed a 40 grade oil. The custom oil was loaded with AW far above normal levels. Every UOA that came from that mix was looking good.

"But that's not racing!"

And you would be correct. But it does show that viscosity isn't the holy grail many people think it to be.

 

[CATERHAM]

Originally Posted By: OVERKILL
Originally Posted By: CATERHAM

Their is nothing tougher on an oil's shear stability than racing
and 24 hours of Le Mans among other long distance races is what Mobil 1 0w50 was developed for.


Yet my understanding is that Mobil 1 0w-40 is used extensively in this event.....? Which has a lower VI

LOL! (yes, I'm just bugging you now) Pennzoil Ultra 5w-40 has a significantly lower VI than either of these lubes though, and it is a popular racing oil from what I understand as well.

Quote:
Kind of silly saying MI 0W-40's VI has dropped from the SM (185-187)to the SN (185).


But it DID drop, from 187 to 185, while not a big drop by any stretch of the imagination it was indeed a drop. And coincidentally or not, the SN version is more shear stable than the SM version. And the pour point went up, and the MRV and CCS increased too.

Quote:
Yes we often talk about HTHSV without talking about he oils VI but that's because most heavier oils have VIs that fall within a narrow range but is you want to be precise about operational viscosity at normal operating temp's you should reference the oil's VI.
This is much more important with the ultra high 200+ VI oils since a 60-80 point VI difference between oils will the same HTHSV will significantly lower the operational viscosity at normal operating temp's.
This again is just one trait of high VI oils that most don't fully appreciate.

Unless one has a viscometer in their vehicle the full ramifications of VI will not be experienced by most members.


OK, but most of us aren't using these ultra high (200+) VI oils. And many of our vehicles don't call for such lubes (like all of mine).

And the same goes for many high performance cars like the ones I referenced earlier. None of them call for 0w-20. Most call for a >=3.5cP HTHS euro oil in a 0w-30/5w30/0w-40/5w-40 grade. Of which the VI's are all over the map.

I know you're just trying to bug me.

Yes Mobil 1 0W-40 (VI 185) is used in racing and their 0w50 only has a marginally higher 189 VI (being a dedicated race oil the main difference is a massive increase in ZDDP and moly).

The reason I blend for a high VI oil (my Caterham's oil has 12% 0w50 in it) is to maximize the HTHSV rating of the oil I use for the minimum operational viscosity I want at normal operating temp's while also providing the lightest on start-up.
If I used a lower VI 0W-20 oil, and I have experimented with many, the oil will be heavier both on start-up and at normal operating temp's with a lower HTHSV rating. Consequently maximizing the VI enables me to run both a higher HTHSV oil for maximum temp' temp protection that's also lighter on start-up; the best of both world.

 

[CATERHAM]

Originally Posted By: Tempest
Originally Posted By: CATERHAM
The single most important aspect of an oil is it's viscosity and you can't talk about viscosity without referencing the viscosity index.

A few years ago, member Gary Allan ran some custom made 0W10/20 (depending on how one looked at it) in a car that spec'ed a 40 grade oil. The custom oil was loaded with AW far above normal levels. Every UOA that came from that mix was looking good.

"But that's not racing!"

And you would be correct. But it does show that viscosity isn't the holy grail many people think it to be.

I run a 20wt oil in my track car that is spec'd for a 40wt by GM, a 50wt by Caterham.
Of course viscosity is still very important as you still need to maintain that minimum film thickness to prevent bearing wiping but how much viscosity you need is dependent on oil temp's, amount of fuel dilution, oil shear etc. So when a manufacture specifies what an oil grade they must build in a very large viscosity margin to deal the possibility of the perfect storm combination that could severely thin out an oil.

Of course today OEM have other ways to deal with unexpectedly high oil temp's that can unduly thin out an oil, and they are electronic safety systems that will gradually reduce power until the oil temp's drop. In extreme cases the engine will go into limp mode. This is how Ford manages to specify a 20wt oil for it's 400+ Mustang GT.

 

[OVERKILL]

Originally Posted By: S65AMG
And yet Mobil 1 0w40 has a high VI and is used in racing.


It has a relatively high VI. I mentioned that earlier. It isn't stratospheric like the 0w-20's.

 

[BlueOvalFitter]

Originally Posted By: surfstar
[/quote] Blue - the fuel adds go in the tank, not the sump.

No way......and I was just about to add a mixture to my blinker fluid reservoir.

 

[buster]

Quote:
Joe Gibbs Driven Racing Oils are properly balanced to protect a racing engine. Adding Joe Gibbs Driven Racing Oil to a conventional oil may not enhance the performance of the oil. In fact, adding Joe Gibbs Driven Racing Oil will change the balance of the oil, which could lead to engine failure. This is known as additive clash, and should be avoided

 

[BlueOvalFitter]

Originally Posted By: buster
Quote:
Joe Gibbs Driven Racing Oils are properly balanced to protect a racing engine. Adding Joe Gibbs Driven Racing Oil to a conventional oil may not enhance the performance of the oil. In fact, adding Joe Gibbs Driven Racing Oil will change the balance of the oil, which could lead to engine failure. This is known as additive clash, and should be avoided

Will my truck make left turns only if I use this oil?

 

[Garak]

@buster: Joe Gibbs oils cause wallet clash.

 

[S65AMG]

Originally Posted By: OVERKILL
Originally Posted By: S65AMG
And yet Mobil 1 0w40 has a high VI and is used in racing.


It has a relatively high VI. I mentioned that earlier. It isn't stratospheric like the 0w-20's.


Yep and this is what Mobil say about this topic:

"Synthetic oils have higher VI than conventional oils

So, synthetic oils provide better engine protection across a wider range of
temperatures

At more extreme temperatures, the benefit becomes greater"

 

[OVERKILL]

Certainly. But they are speaking of the natural VI's of the base oils, not that they are filling their synthetic offerings full of polymer