Which way to 50/50?

[Dust]

I have access to
1. 95%M5%E at 400 yen for 1L.
2. Battery water (distilled?) for 100 yen for 1L.
3. Windshield wiper fluid, no bubbles is 185 for 2 liters at 40% methanol,
4. Bubbly fluid at 45%M, 175 yen for 2 Liters and
5. no bubbles 50%M for 400 yen for 2 liters
and I have a brita water filter that is not used for drinking.

I just lost an IAC valve at $400 and I feel, without seeing it, that it got some residue in it and caused it to short out. So i am looking at maybe running something safer for my car parts. I have been back and forth between 25 and 50% meth, but being that I have 64 hp(government mandated), even with upped boost, I can't really feel a difference in the two. 25% meth would obviously allow me to spray cheaper. What mix and what fluids should I be using?