Too much logic and facts, so let's stick our heads in the sand and pretend it's not there.
From an engine builders perspective of why headgaskets fail. And let's be nice and call it "mislabeled fuel" instead of negligence. - Uncovering the Culprits That Cause Head Gaskets to Fail - Engine Builder Magazine
Wow, thats a fascinating article, thanks for posting. 80 series 1FZ-FE owners really need to read that!