I also used Penofin. I used the Marine Oil variety as it was suppose
to have the highest UV protection and I love the look of the redwood
and want to delay the greying effect as long as possible.

I was told that it will eventually grey -- not much you can do to stop
that.

The only thing I found about oil is to not use things like BLO and
stick with oil that has been treated with antifungal and UV inhibitors.
Linseed oil will mildew in the moisture it is exposed to outdoors.
Maybe true with other oils that are intended for indoor applications.

I only did this 4 months ago so can't report on the grey fading however
I pretty much concluded there is little that will stop that eventually.
I kind of like the grey anyway -- only don't like fungus / rot look.