Reading various info on the net then DOT4, DOT4 ESP and DOT5.1 are all compatible for use in DOT4 systems and can be safely mixed.
Where DOT4 ESP seems to differ from DOT4 is in that it has a lower viscosity and therefore will be (in theory) more responsive at lower temperatures which will potentially aid/enhance an ESP's fine control operations.
I'm concluding / deducing the following:
1) With normal braking then the driver is applying a constant and steady force
2) With ABS then when 1) causes the wheel(s) to lock then that wheel(s) is automatically released and then braking applied again
1) and 2) are essentially an On/Off application of a fixed hydraulic pressure.
3) With ESP then the system is continuously dynamically modulating/adjusting the hydraulic pressure and attempting to do a "fine" control. The blurb is suggesting that this fine control is affected by temperature and viscosity and the ESP formulation can aid the ESP's performance at lower temperatures.
Seems to make sense but how much difference is made is not discussed or comparative data available.
For most people I guess ESP deploying is hopefully a last resort get me out of trouble. For racing/track work then things change a bit and the ESP system is probably working overtime and an experienced driver of/under these ESP operating conditions might? find a difference between DOT4 and DOT4 ESP.
