Science of VII dosing for Multigrades

[MarcusB]

Hi there My first post, so go easy on the newbie please!! About viscosity Index Improvers... I understand the working mechanism of the VII to be that the polymer uncoils at increased temperature which effectively boosts the oil's apparent viscosity. Also, the greater the VII dosage, the greater the VI increase (wider viscosity stretch). Therefore, I believe the lubricant grade can be formulated by using the correct amount of VII relating to the product, and then balancing the base oils to achieve the target lube viscosity (cSt at 100degC using standard tests). However, manufacturer's recommendations for treat rates is limited, my enquiries to them have been rather frustrating, and I've turned up little of assistance on google. Hence I'm appealing to the board for assistance in my understanding of application of VII to wider grades! For instance, one well known manufacturer produces a copolymer in solid form, which it recommends to dose at 12.5%wt into SN150 base to produce a VII masterbatch. It then provides treat rates as follows: 5W-30: 10-11% 10W-30: 9-10% 10W-40: 10-11% 15W-40: 8-9% 20W-40: 7.5-8.5% This is ok, and I get the general idea. But what is the science behind it? How does it relate to J300? Is the treat rate % related to the resulting viscosity index of the finished blend? I would rather understand how to calculate (rather than guess) the treat rates for eg. 20W-20, 20W-50, 0W-30, etc. etc. Also what about treat rates for multigrade gear oils, eg 80W-90 and 85W-140. Finally, regarding base oil blending, I've discovered that applying the masterbatch V100 as 1,450cSt (per manufacuter's data) to the tested base oil blends (say SN150~5 & SN500~11) - the theoretical viscosity (from weighted average logarithms) gives a very good approximation to the tested viscosity. So I must be doing something right!!! Thanks in advance for any input. Best Regards, Marcus

 

[yvon_la]

VII AND OTHER similar is probably a loophole .back then api wasnt as vigilant .even today corp chaffe and try to wiggle their way in(trying to make some believe their group 3 oil is a group 4,or better?their group 3 is a group 3+ (rofl)why you think api said no in single weight oil .its better?nha ,just that someone on that side was more vigilant and caught it in time.i suspect the next oil standard will be using a lot of page from sae 30 book.why you think oil corp shy away from sae 30 certification for car or truck?it is a lot more work.i dont think api will let slide next .if they do?gf-6 likely wont !or pc-11 wont

 

[MolaKule]

Quote:

But what is the science behind it?

When formulating to specifications the first thing one has to do is examine the application: PCMO; HDD, gear lube, etc. The specifications should guide you toward the target viscosity. When using any base oils (mineral oils or synthetic), one decides which base oil or mix of base oils (which is usually the case) is required to attain the virgin viscosity, viscosity range, and viscosity index. The PI package has a certain viscosity as well, so that affects the final viscosity. Once the base oils and PI package are blended, you then test to see what that viscosity and viscosity index is. THEN, you treat the PI and base oil mix with a certain percentage of VII to attain your targeted viscosity and VI, and test again. One must use Groff Charts or computerized Groff Charts throughout the development process to get the targeted viscosity. The manufactures treat rates are "SUGGEESTED" treat rates for a specific base oil mix, so your formulation will differ as to final VII treat rate.