List motor oils based viscosity index?

[OilUzer]

Originally Posted by Onetor
Is there a current list of motor oils based on Viscosity Index? I hope that question makes sense. Thank you!


First you must compare same grade oils for example comparing vi of 5Wx30 with 10Wx30 does not make sense!
Obviously in general 5Wx30 will have a higher vi than 10Wx30. Higher vi doesn't mean it is better. If for example 10Wx30 meets the application and the W rating, I wouldn't worry about its low(er) vi. Actually I am now concerned about high vi oils

with some exceptions (see below).

VI is an overrated parameter! That was my initial thinking once I learned what it really means. Shannow explained vi in one of my threads regarding this subject ... and further research confirmed my initial thinking that it is overrated. Not saying experts agree with me but this is just my conclusion to the point that I don't pay as much attention to it as I used to! It's just a mathematical calculation and slope of viscosity graph/curve. Not a big deal.

The only exception is and I did limited research and then kind of stopped for now ... exception is if an oil has a naturally higher vi. For example synthetic oils (with higher group base oil) will have higher natural vi over lower group base oil or conventional ... natural high vi is better than a high vi with too much vii. also I think anything with 0W in it has? a better base oil ... I was researching 0Wx30 oils vs. 5Wx30 or 10Wx30 for this exact reason but it's on the back burner for now

 

[oil_film_movies]

It does appear that heavy use of VII chemicals, like that found in 0w40 or 0w50 oil, can create some problems in upper cylinder & ring wear, from the study Shannow cited above.
Another study of cold starting HD trucks showed a definite advantage in startup wear from low visc oil compared to high visc oil, which is no surprise to most people.

Taking both scenarios together, I'd say in the winter go ahead and go with the thinnest oil you can, and it may be better in the summer to switch to something with less VII for better upper cylinder wear & ring wear.
That means there is a start-up temperature where, overall, considering total wear, during both cold & hot oil, overall wear is equal between a thicker oil and a thinner oil.

It comes down to how the engine is used.... Lots of cold starts?-->Thinner is better. ... Taxi-cab usage where it runs a lot or OTR long trips (trucking or vacation or long commutes)? --> thicker oil is better

I'm going a little thinner this winter for cold start flow, still in spec (0w20) though, and with a boat-load of moly formulated in this oil. HTHS is a very standard 0w20 amount of 2.7, which should support most areas in the engine.
It could be the high-moly oil I'm using counters any hot-running higher wear rates in the upper cylinder and rings that might happen. Could be why my Japanese oil formulators went to high moly in the first place. They have a strategy, whatever it is.

Originally Posted by Shannow
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4901760/1