Well, there does seem to be legend, myth, mystery and lies on this subject. The story WAS that it was all about oil and the difference between EU based spec and Asian spec oils. The calcium or magnesium (whatever) was being leached out of the white metal. From my background in metals I can tell you that this is entirely plausible if not actually the case in this instance. It goes on to say that Toyota recognised this and changed the specs of the shells and it was no longer an issue hence the 24 valvers not suffering. Some people have debunked this theory in more recent times, but it matters little. Any 12v that hasn't been changed that comes to live on my drive will have the BEBs done before anything else.
If and I say IF the story about oil spec were true, probably the worst thing you could do would be to change your oil more regularly. As the metal dissolves into the oil, the concentration goes up and leaching would presumably slow down. Fresh oil would therefore be more aggressive.
Hey, I dunno. Without some accurate oil analysis it's all supposition. But something caused it that's for sure and now it doesn't. End of. Someone did post some actual facts once IIRC.
