As curious "child" I measured it with a digital thermometer:
70 ° setting -> measured: 72 °
80 ° setting -> measured: 80 °
90 ° setting -> measured: 89 °
more you can probably with the best will not expect .. I was amazed how well the device works.
For lovers grade "sensitive" teas such as green tea in my opinion, perfect.
Whether softener in plastic (such as a customer in a review I read somewhere guessed) I can not judge, but would somehow make no sense - for which plasticizers in plastic is not touched? I for one think rather that Bosch since even watching ..