Since last April, I have put almost 8,000 miles on my 2020 WR250R.
Earlier this week, I had pumped out what must have been the OEM fork oil as I got the bike with some 700 miles on it and while I was at it, I had greased up the steering stem bearings.
I had gotten about 460 ml of oil out of each fork leg and had replaced it with 2.5wt Elf fork oil I got from Amazon.
I was able go go for a great night ride last night and was thrilled at how much smoother the front end was over everything. As it is so easy taking off the front wheel and the fork legs, I'll probably be changing the oil every 1,000 miles or so, maybe 2,000, to keep the same great fork action that I now have.