Not sure where "here" is, but counter-intuitively (in US and much of Canada - where it has to be labeled) mid-grade is just low-grade + ethanol (which boosts octane), so it's often a down-grade over low-grade (important when you run a carburetor). Grade.
Canada, but I should have checked the current state of affairs before posting - it actually looks like no grade is no regularly available without added ethanol.
