I have 2002 Accord dx non-vtec auto, it has 50500 on it.Its history has been pretty good i suppose. My first 5000k since i bought it new, i change it from factory conventional to castrol gtx 5w30 till up to 12k. Then I ve been running through Hondas 5w-20. I had a engine flush using the bilstein machine that used a "safe solvent", so at that time i was under the assumption that my engine was clean. Up until maybe 25k to 30k, my engine felt sluggish. 10k miles later i stumbled on auto-rx, i added 6oz to the honda oil that i had in there after doing 3k and dirty filter so it will start doing a little cleaning. I drained the oil, then started the official auto-rx treatment. Now for the rinse phase, i ran the oil up to 6k miles instead of draining at 3k, then I switched to Mobil 1 Extended Performance 5w30. The question was that since I only saw some vible varnish, how long would it take to have a perfectly clean engine compartment with adding the 2 oz of LC? I hope the switching to full synthetic and changing the pcv valve would bring a quieter engine.