whats best for thermo modified wood?

Anyone have experience or recommendations on maintaining thermo modified wood?
I have a 4 year old deck built of therm modified wood which has held up beautifully so far with no warping or cracking, but the original dark color is starting to fade a bit. The maintenance info that came with the product said to use an oil-based UV protectant, but should I look at one designed for hardwoods or will a regular one work? I definitely want transparent finish as the wood still has a beautiful dark color to it and I don't want to cover the look of the wood grain. Thanks