Non-linearity when blending oils.

[Shannow]

For reference, Back in the day, when Oz was moving towards unleaded fuels, and we still had leaded available, we used to blend premium and leaded, 50:50 to take advantage of the non linearity in lead content versus R.O.N increase to make a fuel that was "greater than the sum of it's parts".

It's a concept that has been hashing around for a while with me, when people talk of blending resulting in a dilution of everything (potentially), and being a bad thing... to me, small doses tend to give a better "per treat rate" affect than larger...diminishing returns.

Bought some Mobil 1 5W-50 today (Full Synthetic at $7.50/L is not to be sneezed at), and it had me thinking about the calcs in the 5W-50 VOA thread, and specifically how blending this oil with (say a 5w30 would play).

Started again with the Afton HiTec 5710 PDS.
http://www.aftonchemical.com/ProductDataSheets/Lubricant Components/HiTEC-5710_PDS.pdf

because it's usefully complete, and has specific base-stocks with 5 and 10% VII treat rates.

Used the widely accepted Widman blend calculator.
http://www.widman.biz/English/Calculators/Mixtures.html

Logic is that there are two oils, one defines as the 0 treat rate, and one the 10% treat rate...a blend is obviously 5% treat rate...

Using the 100N basestocks
0% treat rate KV40=20.2, KV100=4.1, VI=95
10% treat rate KV40=61.1, KV100=13.7, VI=234

Mix them 50:50, and the calculator gives
KV40=34.4, KV100=7.62, VI=200

Afton lists the 5% mix at
KV40=37.06, KV100=8.05, VI=199

So viscosity wise, the mix of two finished oils, same base-stock,same VII in this case is 5% thicker than the "sum of it's parts", or the linear interpolation of them.

Just for thought.

 

[Tom NJ]

Viscosities blend on a log/linear scale, so a blend will not match a linear interpolation.

In addition, blending dissimilar chemistries (e.g. VII and base oil) often gives a VI synergy where the VI is above the linear interpolation and varies with dosage, which shifts the viscosity plot.

I imagine the Widman calculator only addresses the log/linear relationship but not potential VI synergies since the calculator does not know the formulation.

Tom NJ

 

[andyd]

OK, I'll take your word for it. I try to use up old or left over oils as I go. My main concern with oil has boiled down to maintaining the level between changes. I dont even change out the 20w50 in cold weather any more. I just pour in a pint of MMO to lower the viscosity a pinch and get some cleaning to boot.

 

[A_Harman]

That's thing about chemistry that bugs me. Synergistic effects lead to unpredictable outcomes. The chemist really needs to know the nuances of the chemical systems he's working with.

Oh, the panoply of ecstasy that is organic chemistry!

 

[Shannow]

Originally Posted By: A_Harman
That's thing about chemistry that bugs me. Synergistic effects lead to unpredictable outcomes. The chemist really needs to know the nuances of the chemical systems he's working with.


Hmm...given that the Afton case was single base-stock, and "blending" gave different results, it's an interesting though, isn't it that given same base-stocks, two oils with "different" VIIs would/could display double the effect.

Would make blends calculated with any of the calculators or log worksheets more viscous than the proponents would otherwise wish to believe...

 

[Clevy]

After reading some of the posts the other day I'm rethinking my idea of mixing brands and using additives altogether.
Finished lubes really are a careful and delicate balancing act to achieve an end result. Sure I like to experiment but I've come to the conclusion that I don't know enough about what I'm mixing together to conclude whether its a positive or negative.
I really didn't realize how delicate the balance really is. I'm glad we've got members who take the time to inform laymen like myself.
Thanks Shannow,you are certainly one of the wealthy of info we have here. I appreciate your effort in helping me understand many things and help me to see the entire picture and not just one piece.

 

[buster]

Originally Posted By: Clevy
After reading some of the posts the other day I'm rethinking my idea of mixing brands and using additives altogether.
Finished lubes really are a careful and delicate balancing act to achieve an end result. Sure I like to experiment but I've come to the conclusion that I don't know enough about what I'm mixing together to conclude whether its a positive or negative.
I really didn't realize how delicate the balance really is. I'm glad we've got members who take the time to inform laymen like myself.
Thanks Shannow,you are certainly one of the wealthy of info we have here. I appreciate your effort in helping me understand many things and help me to see the entire picture and not just one piece.


I agree. I've never been a fan of mixing oils with different chemistry. You're just creating an unknown mixture. Playing chemist without any tools to tell you what you end up with is not something I like to do.

Thanks Shannow & Tom for those comments. Interesting.

 

[TrevorS]

This is what Mercedes have to say about mixing oils and additives in the current sheet 219 document.

Its interesting to consider whether mixing MB approved oils across brands would also be a no no. You might expect those chemistries should be compatible with each other.


Originally Posted By: MB Sheet 219.0
Only oils that are ready-formulated ("doped") and tested are approved for operating vehicles, engines and major assemblies. These ready-formulated lubricants are made from selected base oils (such as mineral oils, hydrocracked oils, PAO and ester) by mixing it with oil-soluble chemical additives.
In addition to the lubricating effect, these products have all the properties for optimal operation that are required of a good lubricant nowadays. Examples of these are wear and corrosion protection, detergent capability, cleansing effect, neutralization capability, dispersing capability (protection from sludge formation and deposits), aging resistance, corrosion protection, pressure absorption capability, foam inhibiting, cold flow capability and many more. The various additives in the ready-formulated lubricants are coordinated to each other and are properly proportioned.
Different companies supply products that have to be subsequently introduced or mixed into a ready-formulated lubricant and are intended to improve the characteristics of the lubricant. These additives are referred to as "Special additives" in the following in order to make a better distinction.
The following effects are assigned to special additives by the companies (or sales persons):
• Low friction, i.e. lower fuel consumption
• Reduced exhaust and soot emissions
• Longer oil change intervals
When a new engine, major assembly or vehicle is being developed, the spectrum of activity of the lubricants is investigated and analyzed in expensive series of tests in the laboratory, on the test stand and in the vehicle. The lubricant and the additives are tailored to the requirements and stresses that occur in close collaboration with the lubricant manufacturers. The ready-formulated lubricant is not approved by Daimler AG until successful testing has taken place. The approval is canceled whenever changes are made to the tested product.
If special additives are added in an uncontrolled manner there is a risk that the sensitive balance of base oil and additives is upset and the carefully balanced properties of the lubricants are worsened. Daimler AG has no direct way of influencing the type, quantity or handling of the special additives and checking each individual usage case.
Up to now Daimler AG has not approved any product that is allowed to be introduced or mixed into approved, ready-formulated lubricants for engines, transmissions or major assemblies in Mercedes-Benz vehicles as a special additive!
The vehicle owner is solely responsible if special additives are used in lubricants! If damage occurs the legal warranty and guarantee claims may be limited!