Hello! Last summer I discovered a whole bunch of oil sludge in my engine and then tipped a cleaning additive into the oil, drove about 300km and then made an oil change myself to run the whole mud thoroughly. Have used Valvoline 5W30, is that good? (so I mean the oil mark, 5W30 is recommended) Now I have the same problem again. Sludge where the eye goes. I can do it again now, but I wonder why m What can I do about it and what are the possibilities for cleaning the engine? I probably wouldn’t have noticed at all, but my engine always has speed problems with which it almost drains me. I drive the MK VI 1.3L, that’s the HCS engine. He has this flutter or Novo valve in the air filter box that also muds and therefore doesn’t work properly anymore. Conclusion: Oil in the air-gas-mixture… that doesn’t burn well, of course. And the car eats oil without end. Will now change the valve first. I also changed the oil filler last year, because it was also muddy. Thanks for your tips in advance.