Originally Posted By: surfstar
Originally Posted By: Jetronic
Originally Posted By: TiredTrucker
Probably because a 10w30 usually has a lower NOACK rating compared to 5w30 of the same brand, along with fewer Viscosity improvers. Some full synthetic 10w30's have no need of any viscosity improvers. All of that a plus in some folk's books.
Would you say that's a minus in your book?
I thought lots of VIIs were beneficial for short tripper and cold starts, mainly?
I've always liked the [spec/data sheet] #s syn 10w30s gave. And now my VW uses 0w40 - widening the gap both directions.
VII polymers are both a blessing and a curse.
In the 50's, when all you had was relatively low VI solvent extracted base oils, VII's were the thing that allowed you to have the same grade of oil in both the winter and summer. Back then engines were rudimentary and the only anti-wear additive was ZDDP so you definitely needed oil to be thick at operating temperature to avoid wear. Given that oils were changed after a few thousand miles, the downsides of using VII polymer (primarily deposits and higher Noack) could sort of be overlooked.
Fast forward to 2016 and things are very different. Base oils are far better than they used to be. In terms of use in engine oils, Group I's are already dead and buried in the US. Group II/II+ is the norm and this is supplemented with Group III, PAO & Esters. All these have better VI and massively better oxidative stability. Additives have also evolved to deal with the deposit problems caused by VII.
However the outcome of all of this is a bit perverse. We use better base oils and higher treat rates of better additives yet we still use VII in much the same way and at the same treat rates as we did back in the old days. 10W30, the old standard US grade morphed into 5W30, 5W20 and 0W20. You can just as easily get 5W40 and heavier. The country didn't really get colder. It's more the case that low temperature performance became a tool for OEMs to get FE/emissions credits. Interestly, the lower the X-rating, the wider the cross-grade, the more VII you need and the more DI (especially ashless dispersant) to need to counter the extra VII. The final kicker is the fact that all of the above drives up Noack which is increasing a problem for 2016 cars; especially GDI's.
The way I see it, if you narrow the cross-grade you take out VII, that means you need less DI which overall gives you a cheaper and lower Noack oil...something like a 10W20..
Hope that helps.
