When I originally purchased the same fuel tester the motorcyles were using for the cars; it came with a complete listing of the contents of the fuel and what it should read on the meter. 3 or 4 guys trained on it including me. At that time we would ask the entrant the name and grade of the gasoline, look it up on the list, and test it. If it came out where it should on the listing you were legal.
One specific thing it said was never to mix different brands or different grades of the same brand..
I had to empty my tank this week because I don't have enough ERC A19A for the November meet and need to buy some VP to make sure I have enough. (I can get VP locally)
I do not know what they are currently doing to test gasoline ant El Mirage because I haven't made it back in, hope to in November..
Good Luck......