So, i've been doing all of my tuning on devil's own brew which is very close to 50/50. I have had the system installed about a week and I am on my 3rd gallon of mix. Now, once it all gets dialed in, my usage will go down significantly as I wont be making pull after pull. Anyway, I could switch to washer fluid but i wonder how that will affect my tune.

 

Depends on the mix, but some of the colder freezing point washer fluids are up to 40% meth. IIRC, the lowest was still 25%. There is a table or chart of the well known brands floating around with ratios, maybe on here somewhere.

EDIT: Here's the thread. https://www.miataturbo.net/forum/t6885/

I guess my point is if you are in the 40% range, it can't change much.

 

You live in southern Indiana.

I seem to recall that they have some auto racing going on there.

Where there's racing, there's race fuel.

VP, WorldWide, and no doubt several other makers of racing fuel sell one or more blends which are 99.95% or higher pure methanol. In CA, I was paying about $6 a gallon for VP brand M1 at my local speed shop.

Take it home in a 5 gallon plastic jug and mix it 50/50 with distilled water. Add a drop of red food coloring if you want to.

In total, you'll be paying ~$4 a gallon.