That MTBY is used by law at certain times of year in Massachusetts. Big controvery over it as it has been blamed on reducing fuel economy and blamed on being about a toxic as arsenic and get into the ground water. For that matter so did tetraethyl lead to enhance anti-knock and I do recall the owner of the company that made it screaming when "unleaded" became law. He claimed lack of it would destoy your engine and was a valve lubricant but it was all lies.
Lead in gas was a cheap way to make higher octane with low grade fuel. It takes a higher percentage of crude oil to make better fuel so if you recall unleaded cost a touch more than the leaded. It's hindsight but lead never belonged in fuel, T
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Tom Greenleaf - MetroWest, Boston