I may be wrong on this but - when I had a part ownership in a skydiving
airplane (Cessna 206) which used 110 avgas you could not store it more
than 3 or 4 months (we had a small tanker truck) before it would start
breaking down. More important for an airplane obviously but would not
help performance n a race car either. We would send in gas and
oil samples
periodically for analysis and thereby learned about the gas breakdown.
It would be a bummer to learn that that drum had gas you couldn't use
for racing, couldn't use in a "modern" car but would have to burn up in
something like a Cobra.