based on the Hildebrand solubility theory, which considers the cohesive forces between solute and solvent molecules, there is a general trend that as the viscosity of a substance increases, its solubility tends to decrease. This relationship holds true for identical substances, such as same-family (e.g. paraffins, saturated) hydrocarbons.
, leveling accusations against me that defy imagination Yes, it's minor and doesn't make or break anything in the operation of an engine. Bearings are not going to be damaged or fail because the oil becomes slightly hotter with a thicker oil. Also, as mentioned earlier, the bearing clearance has a lot to do with the temperature rise inside the bearing, regardless of viscosity, so other factors are involved. Even if there is slightly more oil temperature rise from using a higher viscosity oil, the advantage of more MOFT is still prevalent, and why using a thicker oil for track use or other demanding conditions is the direction to go to ensure adequate engine wear protection.
Obviously, thermal control of the oil temperature also plays a major role. Cars designed with effetive oil coolers can get by better with a thinner oil in demanding use conditions. But some high performance cars still specify a thicker oil, even though they also incorporate effective oil coolers (ie. C8 Corvette specifies Mobil 1 ESP Formula 0W-40). It pretty much comes down to how much film thickness headroom the engine designers wish to incorporate into the design.
We all know that oil viscosity changes with temperature. It doesn't take "excessive heat" to lower the viscosity. The viscosity is lowered inside the journal bearing as it shears and heats up in the supporting hydrodynamic wedge. Bottom line is that thicker oil will always provide more MOFT, even if the oil heats up a bit more inside the bearing because the viscosity inside the bearing is still greater than with a thinner oil. A thinner oil also makes the MOFT smaller, which in turn makes the shear rate of the thinner oil increase, which also makes it heat up more. That's why the difference in oil temperature rise vs viscosity isn't very much and is really a non-issue. It's just a misconception that there's some giant difference and that a thinner oil is going to magically make the sump temperature less. I've ran different viscosity oils in the same engine, and the sump temperature sensor didn't change in any noticeable way.
(friendly) Even if someone did see a slight decrease in oil temperature with a thinner oil, it doesn't mean that it's providing better engine protection because the film thickness between moving parts can still be less than a thicker oil at slightly hotter temperature - again, this is why thicker oil (not thinner) is specified for track use and other demanding use conditions. How much difference in oil temperature are these people claiming? Got links to their chat board claims?Your personal experience is indeed valuable in contributing to scientific knowledge. It's important to continue observing and collecting data with your precise sensors
However, it's worth noting that there are differing opinions on this matter expressed on various forums. Many individuals have reported experiencing improved heat transfer when transitioning to low viscosity oils.
And exactly were inside an engine do you believe this "enhanced self flow" (due to gravity) is going to be providing better lubrication? And under what conditions? Like explained before, when the oil is hot there isn't enough "self flow" difference to make any difference. If the oil was at -25F and not the correct "W" rating for the conditions (when it should have been), then there may be some notable differences.
Tolerances are tighter.Well, thoughts of mine then
When it comes to lubricants viscosity, there are several important aspects of engines to consider. As mentioned before here, one of the main challenges lies in refining surface roughness and reducing bearings clearance.
Over time, clearances have generally decreased, with German engines holding no particular disadvantage over American or Japanese motors in this regard (Why they need more viscosity?? Please abstain from expounding upon temperature, for the question served but a rhetorical purpose.)
Now, let's explore the significance of viscosity reduction and its impact on engine oils.
By using oils with lower viscosity, we can achieve a few benefits. Firstly, the oil flows down more easily, which is a small but positive advantage. Secondly, and more importantly, lower viscosity oils have greater solvent capacity.
In modern engines, issues like oil coking and piston ring sticking have become common. These problems can be attributed to various factors, including the quality and viscosity of the oil. While the amount of polymer & additives in the oil plays a role, it's not the most critical aspect. It's possible to produce SAE40 oil with a small amount of polymer, but for certain applications like PCMO in winter, mineral 600 base oil without polymer is not suitable.
So, Law: when we decrease viscosity, we enhance the solvent capacity of the oil due to the physico-chemical properties of liquids. I am comming to realize that there is no need to embark upon a daunting search for identical oil series, meticulously comparing their D611 and D1133 characteristics, It suffices to say that reducing viscosity leads to increased dissolving capabilities. But I guided by the profound wisdom encapsulated within two fundamental equations: [Stokes - Einstein] and [Nernst - Brunner]. Should you desire, I am more than willing to share the some insights of these revered equations.
Boosters like esters can be used, but they also tend to provide better results in SAE16 oils compared to SAE40 oils. However, it's important to note that even boosters have limitations. Esters have limitations in PCMOs a lot.
In essence, within a chosen series of oils with similar compositions, lower viscosity oils always exhibit superior dissolving capabilities.
An "average" SAE16 oil can have solvent capacities up to 1.5 times better than a chemically similar "average" SAE40 oil. Moreover, the starting temperature for dissolving forces and optimal dispersibility is much lower for SAE16 oil, often at around 85°C, while SAE40 oil requires temperatures of 115°C or higher.
In conclusion, reducing viscosity can significantly improve engine cleanliness and the performance of piston rings - both crucial factors in modern internal combustion engines.
Now, we must come to terms with a singular truth: contemporary low-viscosity oils are crafted from remarkably tenacious and non-volatile synthetic bases, rendering them impervious to the volatility that plagued thin oils of yesteryears.
Nah…that’s not necessarily true. No “thickeners” are required to meet base viscosity at operating temperature.
Have they tested with air-cooled engines? Since the results will surely be amplified there?
I have no doubt these are valid points. Find F(x) for solvency, and fluidity and compare them to F(x) of MOFT in increasing engine life to see which variable is more dominant. we also need to make a regression analysis after that to confirm the correlation and dependence between the different variables and to reach a conclusion based on statistics and not a bunch of (it made my engine immortal). Until then, this debate will remain theoretical.
When I think about BiL’s 400k on a GM 5.3L/4L60e ? Well, he lived in S. Texas but worked in S. La …
your statement does hold a certain degree of truth. However, I would like to provide further clarification by specifying that my focus is primarily on oils found within the average PCMO market segment. I am not writing into consideration specific oils that are known for their high ester content, which is a subject of ongoing debate. Nor am I referring to specialized big gas engines oils that may not require the use of thickening agents. In the case of stationary gas engines, it is generally recommended to formulate oils with higher viscosity, while minimizing or completely avoiding the use of synthetic feeds - oils based on a viscous mineral base, such as a 600 base oil, are commonly favored in such applications. Etc..
You’re taking a PChem principle, and applying it broad spectrum, while ignoring other factors. This is a mistake.
@ArthurArgentum "SOLUBILITY PARAMETERs
In 1936 Joel H. Hildebrand (who laid the foundation for solubility theory in his classic work on the solubility of nonelectrolytes in 1916) proposed the square root of the cohesive energy density as a numerical value indicating the solvency behavior of a specific solvent.
It was not until the third edition of his book in 1950 that the term "solubility parameter" was proposed for this value and the quantity represented by a delta (). Subsequent authors have proposed that the term hildebrands be adopted for solubility parameter units, in order to recognize the tremendous contribution that Dr. Hildebrand has made to solubility theory...."
Where do you see viscosity in the Hildebrands formula?
The Hildebrand formula had numerous problems with various solvent discrepancies so the Hansen formula was introduced to improve the solubility indices and for more than 50 years Hansen Solubility Parameters, HSP, have proven to be a powerful, practical way to understand issues of solubility, dispersion, diffusion, chromatography and more.
