Hot, warm or cold: when the temperature matters
Heat helps grease and hurts protein. Getting that the wrong way round is why some stains set permanently.
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Heat speeds up almost every cleaning reaction, and dissolves fat that is solid at room temperature. For grease — a hob, an extractor filter, a roasting tin — hot water does a large part of the work before any product is involved.
Protein is the exception, and it is a sharp one. Blood, egg, milk and sweat coagulate when heated: hot water cooks them into the fibre and sets the stain for good. These go in cold water first, always, and only get warmth once the mark is out.
Enzyme detergents have their own window. They are biological catalysts and they denature above roughly 50°C, so a boil wash destroys the very thing you added to break down the stain. Follow the packet rather than assuming hotter is stronger.
And for microfibre, high heat is simply wear: 30–40°C for routine washes, with 60°C reserved for stripping residue. The fibres harden over time otherwise.