The "Low Lead" suffix refers to how much lead it contains compared to previous blends of AVGAS, not motor fuel.
I looked into the use of 100LL AVGAS in my competition car's engine. If I recall correctly, it contains between four and five times what used to be in 4 star petrol. I added one gallon of 100LL to four and a half gallons of unleaded and the car ran very well indeed.