My understanding is that the tetraethyl lead added to gasoline years ago was used to boost octane, but had the unintended side effect of lubricating the valve seats. The octane available in standard gas is now quite high without the lead, and there is lots of evidence that modern unleaded gas does not usually do significant damage to non-hardened seats, but the lead additive is a good way to prevent valve problems. I wonder what the final octane would be for 87 unleaded + lead additive? probably overkill.
By the way- "mid grade" gas is just an in-the-pump 50-50 mix of the low grade and high grade gasoline- If this guy says the low grade gas is crap, so is the mid grade.
-Warren (squarenutz)
