Highly viscous liquids have very high density while lesser viscous liquids possess low mass per unit volume. It relates to the number of atoms or molecules of a substance present in a particular volume. Honey flows very slowly and is highly viscous, whilst water flows rapidly and has a low viscosity.ĭensity of a material is the mass per unit volume or weight per unit volume. An excellent example is of honey and water. Thicker the liquid, more viscosity it possess. As for the liquids, it can be defined as the resistance to flow. Viscosity is actually the resistance to gradual deformation by shear stress or tensile stress. These two physical properties are often mixed up with one another and you should be able to distinguish between them. Density and viscosity of liquids are two properties of matter which are quite similar to one another but have many differences as well. We hypothesized that no significant difference would be found in depth of penetration or presence of RLLs between the two cohorts. All liquids might not have similar sort of physical properties and these differences might be helpful in choosing the right liquid for particular tasks. We compared cement marketed as high-viscosity cement (HVC) with one marketed by the same manufacturer as low-viscosity cement (LVC). Solids, liquids and gases have entirely different physical properties but there are certain attributes which may differ in the same state of matter. I'm thinking what wulimaster brought up may be a key to this: if the oil has a high Noack that makes me think that the oil is dependent upon more VI improver which over time is shearing off, leaving the oil thinner and more volatile and so you get more burn off.Properties of matter vary in its different form and a basic knowledge of these properties can allow you to understand the behaviour of matter under certain circumstances. Logically, that would seem to be the case, but VI merely addresses resistance to viscosity change with temperature.without knowing the blenders "raw material" specs you don't know for sure if he got the high VI with a "magic" base oil or with lots of VI improver. 5W30) can be assumed to have less VI improver. What I don't believe is necesarily true is your statement that lower VI oils within a viscosity spread (e.g. The reason: an oil that depends heavily on VI improver will, over time, thin out, become more volatile and will put contaminants in the oil as the improver shears off and becomes detritus. If you have a choice between two oils of the same viscosity spread you want an oil that achieves the spread with less VI improver. I think the most important thing in your post is the last part. You are correct in your definition and wulimaster was actually agreeing with you until he added the Noack piece.
#High vs low viscosity free
Please feel free to correct me if I am mistaken. Otherwise the Noack would be higher like Mobil 1 and the viscocity at 100C would be lower like Mobil 1. I believe the VI Improvers in the 0w30 are probably the most shear stable in the industry. A lot of the difference in Noack is the amount of VI Improver that is burner off.
Were the 5w30 to be made with the 196 VI basestock you would have seen a lower Noack than 6.9 %. That is why you see Amsoils base oil VI go up as the spread increases. That is if they use the same amount of VI improver. Higher VI base oils can cover a larger spread than lower VI base oils and therefore require less VI improver (modifier).Īlso, lower weight multis (5w30) require a higher VI base oil than higher weight (15w40) multis with the same spread (25). Your first sentence was correct but from there you went 180 degrees off. Ergo, the oil with the lower VI is the "better" oil. Hence, the oil with the lower VI uses LESS VI improvers. When it comes to synthetics, my theory is that if an oil of a certain grade, say 0w30, has a lower VI than the 0w30 of another brand, the oil with the lower VI is relying more on the VI of the base oil blend to achieve the vis spread than on VI improvers. In general, the wider the vis spread of a multi-vis oil, the higher the VI. VI is nothing more than an "indicator" of an oil's ability to resist viscosity change with change in temperature. Does higher viscosity index mean better? Or lower viscosity index mean better for cold starts?
I notice most 10w30s are around VI=150 while 0w40s are around VI=190.
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