Snippet about petrol storage and how quick it spoils,

[Mortblanc]

Why not just put the date of filling on the can. No need for numbers. Grab the oldest can first.

Date and a few drops of stabilizer and you can make a quick deduction. I have kept fuel for several years without it going bad.

I have also found that two cycle mix seems to last forever. It also runs fine in 4 cycle engines, just a little smoky on occasion, but it beats sitting in the roadway empty.