I run Valvoline synthetic. It's cheap, easy to find, and if its good enough for the spec miata guys it's good enough for me. I use it in my miata, though I imagine it'd work just the same in the 2. 4+ hours of track time is typical for the miata per event, and the brakes always feel great. I pump fresh fluid through before each event just to be safe. I haven't tracked the 2 yet, so it still has the OEM fill.