The German housewife is notorious for her scrupulousness and some of it has rubbed off on me.
I wash flannels, tea towels, white towels and dish cloths at 90°.
Coloured towels, underwear and bed- and table-linen are washed at 60°.
Only outer clothes get washed at 30° if dark, 40° if light. Socks with a good dose of disinfectant softener.
I was shocked to read in a magazine that a test had shown that the "60°" eco-cycle on some machines only washed at 27°.
Even though I realise I've probably been a bit brainwashed, I still can't see how 30° can get all infections germs out of anything. As mentioned in a recent thread, it horrifies me that hotels only wash their towels at 30°! I dry my private parts on them and someone else might have dried their feet on the same patch of towel. What if they had athlete's foot? (Or vice versa - I sometimes have sweaty feet myself.....)
I have never understood what a "Biological washing powder" is or does. We don't have them here.
By the way, Esspee, I think the hotter wash cycles probably spin at a higher rate, which is why they crease more.