I don't recall seeing any testing, lots of ad claims though, In my experience after trying one of the said claimants and 3 or 4 other normal hi perf fluids the difference is so minor that I couldn't detect it.

A caveat, every system is stressed to a different extent, both of my cars have full 9933RS brakes and are at the very low end of the stress scale, The only issue I ever had was at WGI where a black flag brought us all into the pitlane which is on a downhill slant, foot on the brake, w/ <50% pads the fluid(ATE200 at the time) began to boil, since then I switched to Motul and throw the pads out before they get to 50%.

The Brembo fluid I mentioned (HTC 64T) has the best peddle feel, especially while being severely stressed, of all the brake fluids I have tried. That includes Castrol SRF, Endless, the Motul fluids, etc.

That feel has a lot to do with the difference in compressibility.

Thanks for the feedback Bill and Scott. I have found I don't like the feel of SRF as much as RBF600 and would consider it "soft" compared to Motul. Subjective at best opinion for sure, and contrary to what others may have feel.

We stock cases of Motul RBF600 and have never had a problem in any of our cars or clients cars on the track. We keep SRF in stock for those that "have to have it".

Cheers

Figured I'd report back after trying it on track. The Castrol felt a bit more consistent on track but not so much that I would realize if I didn't know about the fluid change. Maybe a little less pedal travel when hot. Interestingly enough, it feels much much firmer on the street than the Motul ever did no matter how much I bled it. For that alone I'd say it's worth the extra few dollars.