5W40 or 10W40 in 3B engine?

[Grant Lenahan]

This is a topic  that will engender violent opinions.

But I firmly believe that the most important characteristic of oil is  
its ability to flow when cold.  Most damage occurs when cold.  Shear  
and starvation occur when cold.  Low viscosity defines the oil's  
ability to flow. This is a good thing, unless it should shear.

Furthermore, a 5W40 and 10W40 should have the same high temp  
performance- that's the "40" part.  yes, I'm aware that the spec s  
allow a 10W40 and 5W40 to perform differently at high temps, but its  
still fundamentally a 40weight oil when hot. A more useful m easure  
of its strength when hot is the HTHS shear number anyway.  This is  
best indicated by the presence or absence of the ACEA A3/B3 approval,  
which requires > 3.2.  Note that many oils that miss it are OK too,  
if they just miss it, like Mobil1 5W30 ( 2.9).

Either should be fine, but I would use the 5W40.

If you want more useful numbers than "XwY", look at an oil's data  
sheet and read the viscosity at 40degC (warm) and 100degC (hot).   
then think about what it is when its -5degC (cold)!

Grant
On Feb 24, 2008, at 10:17 AM, 200q20v wrote:

> Fellow listers,
>
> I have been using 10W40 http://www.amsoil.com/storefront/amo.aspx  
> since I bought my car in 03 (280k + miles now). When I got the 12  
> quart case last year I noticed that the label has changed (UPC code  
> has not) and there is no "Volkswagen 502.00, 505.00, 505.01" listed  
> on the bottle. I still used the case for all my cars but this year  
> I decided to do some more research and found that "Volkswagen  
> 502.00, 505.00, 505.01" is listed only on 5W40 http:// 
> www.amsoil.com/storefront/afl.aspx oil.
> Please suggest which one is better for year round usage including  
> one or two high speed events.
>
>
>
>
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