Curious why you would ask this here instead of just doing a web search? If you don't like reading search results, you can just get an AI summary. It's at least as reliable as asking a bunch of internet randos chiming in. Here you're probably more likely to get "10W-40, twice a day" answers over serious ones.
Personally, I prefer 5W and only oil pull once a month.
Because 95% of SE results are either paid in one way or another, or AI generated SE optimized crap mithout meaning.
When I want some actual opinions from real people, I always search "how to X lemmy" or "how to X reddit" (yes thats the only thing I still use reddit for, because it has so many more users)
Maybe spreading misinformation that unscientific home remedies are a substitute for modern dentistry, but that's a larger assumption than I wish to make of OP. I'll just go with good ol', "I forgot Google search exists".