Three hundred degrees
Where do you work - the earths core?
I good truck mount and a good carpet cleaner will clean most carpets between 200/300 degree and about 300/500 psi dave northing breaks down dirt quicker and faster then steam 
I think susan means 300 f not 300 c dave 
300 f = 148.88 c which is classed as super heated water (very hot steam in other words to you and I) 
took from the hydra master web site ore do you know better then them ?? maybe you just need to stop talking about something you know northing about
Water temperature
Perhaps the most significant benefit to cleaning with a truckmount vs. a portable is the high water temperatures truckmounts can sustain. The hotter the water the better and faster results you’ll get from your cleaning chemicals. Some portables have tried to add heaters, but just can’t compete.
If, on the other hand, you’re comparing solution temperatures on competing truckmounts, you should know that it’s not good to rely on the temperature gauge of every machine out there. For instance, if a temperature gauge sending unit is located on or near the heat exchanger, you’ll see artificially elevated temps. Some machines also raise temps by restricting water flow. That’s not good because fewer gallons per minute mean less effective cleaning.
Another thing you’ll want to look for is sustained heat. Many machines out there reach temps of 230 degrees to 250 degrees, but during a typical cleaning cycle (or if a rotary tool is used), the actual temp drops drastically and can take too much time to recover—that causes carpet streaking. HydraMaster truckmounts are designed to maintain precise temperature control with minimal variation, so you're assured optimal sustained heat at all times.