'straight meth' mixtures

[luke2152]

So I've decided to go down the path of pure methanol and lots of it (for fueling purposes mostly). To that end I was wondering if mixing a small amount of water in would make sense:

1. It would stop the methanol absorbing extra water from atmo ie. stay a predictable mixture.
2. Have a bit of anti detonation properties as well.
3. I know the system is supposed to be able to handle pure methanol but would it be more durable corrosion wise with a slightly diluted mix (or would the water indeed be the corrosive element?)

All 3 reasons are not my priority but did cross my mind. If I'm planning on running straight meth, am I better off giving it 5% or 10% water?