I had an extremely slow kitchen drain recently where a liter of water took a couple hours to drain. Every week I poured boiling water into the drain pipe that came out of the wall (bypassing the trap), waited ~30-60 min for the temp to drop a bit before giving a dose of enzyme-based cleaner so the enzymes had a warm start and could chow down on whatever was in there. After a month or so there was no noticeable progress. Snaked it. The snake made it all the way to the main pipe but strangely did not clear it. So I poured in ½ liter of sulfuric acid and let that sit for hours. Still not clear. Then I plunged the line with the acid in it using the kind of plunger that attached directly to the pipe. That cleared it. I have no idea what the clog was.
Now I run the dishwasher on the highest temp as a preventative measure. The lowest temp (50°C) is good enough for the dishes but I figure the highest temp (70°C) will help maintain my crappy kitchen drain pipes. It’s unclear to me if I’m wasting energy or being sensible. IIUC, the 70°C temp setting is for pans (which the dishwasher maker expects to be greasy). The clog that I cleared was from the previous tenant (a young student, probably careless and not knowledgeable about drains). The only grease or oil I put down the drain is residual after a bulk of it goes to the compost.