Originally Posted By: Gokhan
Originally Posted By: CATERHAM
Originally Posted By: sir1900
Originally Posted By: Hokiefyd
A Group III syntactic 0W-20 has a NOACK of about 14% vs. the slightly less than 15% NOACK of a conventional 5W-20. Therefore, in terms of the quality of the basestock, there is not much difference. Group IV formulations will have less NOACK and higher quality. For 5,000-mile OCIs, there shouldn't be any problem.
If the 5W-20 is synthetic and under the same oil line (such as Mobil 1), it will have a lower NOACK than 0W-20, which means that it's made of a higher quality basestock that will allow you longer OCIs and more protection against wear and sludge. That (lower NOACK, hence shorter OCI because of faster oil cooking) is exactly the reason why Mobil 1 Extended Protection isn't offered for 0W-20. Unless the temperature is very, very cold (well-below freezing), chances are that you may even be better off with a 5W-20 synthetic than a 0W-20 synthetic.
First you don't exactly know the NOACK of most 0W-20 oils or what their base oil composition is.
Anyway for the sake of argument lets assume the NOACK is indeed higher for a 0W-20 synthetic vs a 5W-20 synthetic (a product btw that is unique to NA only) that doesn't mean that lower quality base oils are used but rather lighter base oils. So you really are comparing apples and oranges.
And the lightest oil readily available on the market; the Toyota 0W-20 has a recommended 10,000 OCI in the States and we've seen plenty of decent UOA at that interval which is plenty long enough for most of us.
And the main purpose of the high VI 0W-20 oils like the Toyota 0W-20 is all about a low start-up viscosity as possible even at temp's as high as 100F which is still a cold start as far as an engine is concerned. The fact that these oils also work well at extremely cold temp's is actually incidental to their main purpose. It's all about a high VI which primarily is to save fuel but having as oil as light as possible has many advantages.
The following video is about Sustina 0W-20 with it's 229 VI and demonstrates the advantage of a high VI oil quite nicely:
http://www.sustina.us/product-line.php
If you can, fast foreward through the first 1/3rd of it.