I also agree based on common sense, but not on actual knowledge. 5 gallons of leaded gas will do nothing, 50, 500 maybe. The only real threat would be to damage from pinging/pre-ignition/detonation IF that even would happen out side of what the computer would compensate for. So real world worst case, no issue, possibly MORE horsepower if no pinging and better mileage, since the lower the octane, the higher energy in the fuel. (a fact that is hard for many people to grasp)