Fluence Knocking Combustion

Sounds like pre-ignition, which isn't good. Have you tried using a higher octane fuel lately? It could also be carbon deposits in the cylinders. Is it a consistent knock, or does it come and go?

I usually use regular fuel. Higher octane, huh? Would that really make such a big difference? And how would I even check for these carbon deposits?

Yes, lower octane fuel can cause knocking in some engines, especially older ones. The deposits in the combustion chamber are a common cause for knocking. I would definitely recommend taking your Renault to a workshop. I suspect, that an engine tuning could solve your problem, but I am not sure.

Thanks for the advice! Took it to a shop like you suggested. Turns out you were spot on about the deposits. They cleaned it all out, and now it runs like new. Cost me 425€, but worth it to get rid of that awful noise and get the power back.