>| With a 5w50 oil, the base stock is 5W with modifiers to make it act like its up to 50W
>| at higher temperatures.
>|
>| The problem is, these modifiers break down over time, even in as little as 2,500 mi.
>| Once this happens, you basically have base stock oil, in this case 5w, which is too
>| thin for pre-1990 engines.

        Is this true of a synthentic as well? I know dino oil burns itself
into varnishes over time, but isn't the "benefit of a synethic that people
mix a bunch of polymeres together that are much more stable in the thermal
ranges seen inside an engine? Or even blend the polymers to change viscocity
to correlate with the needs at specific temperatures? Or is this just a
myth of synethics?

dave