Does oil mixing really work?

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quote:
Originally posted by Richin Chicago: mixing basketballs and golf balls will not give you baseballs!
Are you sure? I always mix Basketball and vollyball to make soccer ball! It works all the time [I dont know]
 
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I don't know the statement you are talking about, but if the explanation needs to be reduced to the level of ball size, then maybe the person doing the learning has a fair bit to go before mixing oils! (And the person explaining should just say: "don't mix")
 

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That's really incorrect. If you mix a 10 centistoke base oil and a 20 centistoke base oil in equal parts you will not get exactly a 15 centistoke oil. But it will be close. When you mix a 5W-30 and a 10W-40 oil multi-viscosities) it gets even more complicated. (I know I wouldn't be able to figure it out) But it will be between the upper and lower somewhere. [Smile]
 
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Very true, viscosity as a function of temperature isn't linear for a given base oil. Thus you cannot merely superimpose (mix) a number of different oils and expect them to display the properties of linearity as one would expect during linear superposition. Certain base oils will thin much more quickly than others, while others will start out quite 'thin' comparatively-speaking, but will retain a much more steady viscosity over an entire temperature range. For example, GC and the XD-3 0W30; these oils are actually 'thicker' than many off-the-shelf 10W30's at operating temperature, yet qualify for the 0W30 grade because of their low-temperature properties. Another way of looking at is by using an extreme example. If you mix heavy tar and sewing machine oil in your crankcase, the resulting mixture, although it might 'add' up mathematically to be an acceptable viscosity, definitely would not exhibit properties required for effective lubrication. To answer the question of the topic: yes, mixing really does 'work', but oil ultimately is oil, and I think you will find relatively few in here who advocate mixing significantly different grades to achieve some specific results. 0W-30 is acceptable top-up oil to a fill of 5W-30. For example, a common 'mixture' recommended here is 10W30 and 15W-50 Mobil1 for LT1/LS1 engines -- the oils are practically identical to begin with, both 10W30 and 15W-50 are within the lubrication specs for the engine, and some people seem to have positive results with respect to valve noise with that combo. Fairly safe if you know what you're doing, but a disaster if you just haphazardly mix widely differing grades without an appreciation of their chemistrys, characteristics, or consequences. [ September 22, 2004, 02:55 PM: Message edited by: pitzel ]
 
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I think the issue Richin is referring to is: Is there a difference between mixing and blending? We need a chemist to answer this I think, are the oil's molecules chemically bound together or are they just mixed........I dunno....... Lukey
 

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quote:
Originally posted by lukey: I think the issue Richin is referring to is: Is there a difference between mixing and blending? We need a chemist to answer this I think, are the oil's molecules chemically bound together or are they just mixed........I dunno....... Lukey
I'm not a chemist but they are mixed. The mixing is statistically even enough that the resulting (macrisciouc) property (viscosity) will atain its final viscosity by a combination of smaller and bigger molesules.
 
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Richin Chicago, I brought up the idea of mixing straight 30W and 5W30 a few days ago and when the guru's were done dissecting it I felt like voluntarily surrendering my username and password to Bob and selling my computer on E-Bay. Like I said on the last entry to that thread: you can't out engineer an engineer if you ain't an engineer.
 
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quote:
Originally posted by lukey: I think the issue Richin is referring to is: Is there a difference between mixing and blending? We need a chemist to answer this I think, are the oil's molecules chemically bound together or are they just mixed........I dunno....... Lukey
From what I can remember from my senior physical chemistry coursework, intramolecular bonding depends upon the the polarity of the molecule, its physical shape, and the potential and kinetic energy of the individual molecules. A concern from a chemistry perspective in mixing oils, may very well be the miscibility of the additives in the overall ternary solution of oil A, oil B, and the combined additives of oil A + B. This is really the reason why often a mineral 'carrier' oil is required for the additives in some synthetic oils -- the actual olefin components are essentially fats and are not conducive to dissolving detergents very well. "blending" can possibly overcome some of this as it could be done with an appropriate catalyst which allows everything to be properly miscible. Obviously someone at home mixing different oils would not be doing so in the presence of a catalyst, so there cannot be an expectation that the final product would be similar.
 
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I can't find the text now but I seem to recall an Amsoil engineer stating that mixing oil of different viscosities will not give you a viscosity between the 2 viscosities being mixed. He said something like these are unique long chain molecules and mixing basketballs and golf balls will not give you baseballs! Anybody else remember this? Does it make sense? I did a search and couldn't find any relevant discussion.
 
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I would be less concerned about the viscosity and more concerned about mixing the add packages.
 
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I think Pitzel is on track, the polarity of the molecules will play a large role in the molecular interaction. If there is a large difference in the polarity of two liquids, mixing will be poor and your viscosity will not be the average of the two. Surfactants can be used to help add in this mixing, but even that is limited. At the same time would I worry about this with adding a straight weight Group I or Group II to a multi weight group I or II? At the base oil level, no, but your viscosity modifiers concentration has been diluted so you need to take that into account. As to the addition of a heavy Ester-based oil to different basestocks, I am not sure. I am interested to hear some ideas on this.
 
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In a mixture you have droplets of individual materials. Think the cloudy brown stuff where you get water and oil mixed. In a solution, it is clear unless something else such as soot or fine divided metals particle is in there. The components are all broken down into individual molecules. Mix fresh, say a Red Line high ester content oil and a pure dino, and they will form a clear solution. It takes a large difference in polarity for 2 hydrocarbons not to go into solution. In the paint industry, we would add more glycerin or other polyol to vegetable oils and heat them up to ''break the oil''. Above 450 F, esters will interchange into all the possible combinations. We would add highly polar methanol to a sample to check. If it made a clear solution, only traces of fully esterified glycerin was left. We could then add the phthallic acid to polymerize the solution. Don't worry about mixing dino with even the most polar base stocks. They are going to go into solution and stay in solution. What I would worry about is mixing a polyol based ester and a multifunctional acid one. In the hottest parts of the engine, they could react forming polymers or even gels. This is catalyzed by metals. All the oil in you engine could turn into one rubbery mass. I have seen 7000 gallon kettles cleaned out with jackhammers. Oops. I don't think things I used to make paint resins out of, belong in crankcases. Likely additive clashes are a bigger problem.
 
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My take on it is that years ago if a mfgr wanted an oil with the properties of a certain 20-carbon oil that they blended enough 15-carbons with enough 25-carbons to give an average 20-carbon oil, and at first it would behave like a 20-carbon oil. As the oil went through 3000 miles of use the lighter componants would vaporize/burn off and gradually the oil would retain more properties of the heavier 25-carbon oil. Depending on the mfgr they would make a narrow or a wider spread of componant oils and would make a name for themselves based on how their particular mix worked out. These days if a mfgr wants a 20-carbon oil they can specifically engineer the oil to be that particular size, or at worst use a very minimal range of molecule wt/size to accomplish the intended goal. Home brewing using 2 different wt/mfgr oils would be more similar to the older method of accomplishing a certain goal. Probably achieves the goal (to a certain degree at first anyway) but as mileage/use increases the result leans more to the heavier end (even if only slightly, current SL oils don't really burn off much at all). I am just using simple numbers here to be easier to explain my thinking, but does it make sense to anyone else?
 
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Well exactly. A few years back, one of the 'technological triumphs' heralded about Mobil1 'Supersyn' over their older formulas was the fact that they were able to develop the appropriate catalysts to ensure homogeneous mixing and behaviour of the polyolefins, the esters, and the alkylated napthalenes. Whether the people at Mobil did this for economic reasons (ie: make more $$$$ by selling a cheaper oil with similar properties), or whether it is a superior lube is entirely debateable, but as the comments above, especially the extreme example of the paint factory kettles is concerned, mixing/blending vastly different additive basestock components is best done under the supervision of a competent chemist and that even competent chemists have been known to screw up.
 
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