On 8/29/2012 9:00 AM, Tom Carchrae wrote:
> I have to ask just how bad is it to use the much more commonly available
> SAE 80W-90 in there?  Or in other words, what is the benefit of these
> harder-to-find oils?

The synthetics run well over wider temperature ranges. Especially
noticeable if you drive in cold winters, as it makes shifting easier.

The Redline MT-90 is a 75W90, so thinner than an 80W90 when cold. I use
it because I've had good results with it in other VW/Audis, it makes my
Vanagon shift well, and works for me (and many others, from reports).

I wouldn't say it's "bad" to just use whatever your FLAPS has on the
shelf (either GL-4 or GL-5/MT-1), but there will be differences in
shifting feel between brands. Sometimes minor, sometimes things like "I
can't ever get into reverse without grinding."

It's the difference between "this seems to work well for lots of people"
vs. "that should work, don't know anyone who's tried, though."

I believe there are quite a few people running Stalube 85W90 GL-4,
because it's a GL-4 and is the only one which seems to be widely sold
through FLAPS (I think NAPA carries it). It's thicker than the VW spec,
so I'd think it might not work well in cold climates.