I once worked for a company where the engineer used to put fuel drain Avgas into his little Standard 10 car. One day we were having a drag on the straight road from the airport into town, he was in the lead and I pulled alongside him in a Holden FB ute which had ceased to be the front line vehicle, he dropped down a gear to gain the advantage over me and all I could see was an exploding Standard 10 in my rear view mirror.
Lesson Avgas and a Standard 10 are not a good mix!