As long as its DOT 4 or DOT 5.1, does the brand of brake fluid that I buy really matter? I'm not racing the bike, I'm just thrashing it on weekends, and sometimes commuting on her during the week if the weather is nice. I do some longer touring/motocamping as well. I can buy some Lucas Oil DOT 4 brake fluid for $5 US today, or I can order the motorex stuff for double the price and pay for it to be shipped to me. Is there any difference??

IMHO, no.

I don't think it really matters but I, for example, have a few favorite brands I like to use in my vehicles. Not sure it makes a real world difference, but in my head, I'm using premium Oil, filter, brake fluid etc.

Maybe in lab tests they prove that its all marketing and I'm an idiot for believing their hype, but at the end of the day, its my money and I'm the one that chooses how to spend it.

On that note, I used to use exclusively Motorex oil for the KTM and now I don't. Your call.

I found the Motorex brake fluid goes dark very quickly, changed to a premium Castrol fluid and have had no issues with discolour.

I don`t think it is contamination with the Motorex as I did cover the reservoirs and found it slowed up the discolour process dramatically.

Lucas is fine. In fact any and all will work.