Yes, it depends on the machine, ambient temperature, inlet water temperature, how long the machine has been sitting, pressurestat setting and a dozen other variables. However, while a Scace is handy, you do not need one to find the proper temperature. All you need is a pen, paper, coffee and time. Adjust your flushing length by taste. Keep notes, flushed 4 seconds past flash boil, waited 10 seconds, pulled shot, bitter and burnt. Next time flush a few seconds longer until you get the results you are looking for. Every coffee will be different and the environmental variables will have some effect, but you will get the hang of it. Dont get hung up on gadgets, all you really need is a good grinder, good coffee, good machine (a scale is handy) and taste.