Gasoline Octane levels vs Winter/Summer grade in New York

I've been putting 91 in my 25 GT Premium and now that gas stations in New York have switched over to Summer Grade (01 June ~ 15 September), I was expecting a minor performance boost as Butane and other additives are removed but I had forgotten about the denser air in the Winter boosting power. Below is an interesting response from Gemini when I asked it to evaluate 87 vs 91 Winter/Summer grade. I've seen HP and Torque curves between different octane levels for the Coyote but I've not been able to find anything WRT to Winter/Summer fuel and temperature effects.

Your Ford Mustang GT is designed to safely run on regular 87 octane fuel, but it requires premium 91 (or higher) octane to achieve its full advertised horsepower**.** The modern 5.0L Coyote V8 engine features an advanced Engine Control Unit (ECU) equipped with active knock sensors. If you use 87 octane, the ECU automatically retards the ignition timing to prevent engine knock, resulting in a minor loss of roughly 10 to 20 horsepower.

Here is the definitive ranking of power and torque for a stock Ford Mustang GT, ordered from absolute worst to absolute best:

1. Summer 87 (Worst)

2. Summer 91

3. Winter 87

4. Winter 91 (Best)

5. ❌ Summer 87 (Worst Performance)

• Thin Air: Hot summer weather makes the ambient air thin and less dense, restricting the mass of oxygen entering the V8 engine.
• Retarded Timing: High ambient heat increases the risk of engine knock, forcing the ECU to aggressively retard ignition timing to protect the engine.
• Power Loss: This combination results in the lowest horsepower and torque output of the four seasons. [1]

2. 📉 Summer 91 (Baseline Rated Performance)

• Optimal Timing: The 91 premium octane prevents knocking, allowing the engine to run its full, aggressive ignition timing.
• Energy Dense Fuel: Summer gasoline blends naturally contain roughly 1.5% to 2% more chemical energy density than winter blends.
• Heat Bottleneck: Despite optimal timing and good fuel, the hot, thin summer air ultimately acts as a bottleneck for overall power. [1, 2]

3. 📈 Winter 87 (Surprisingly Strong Performance)

• Freezing Air Density: Freezing winter air is highly dense and oxygen-packed, which naturally acts like a mild, natural "supercharger" for a naturally aspirated engine.
• Natural Knock Protection: Cold intake temperatures drastically cool the cylinders, reducing the engine's tendency to knock. [1]
• Timing Penalty Overcome: The ECU still pulls minor timing due to the 87 octane, but the massive power gains from dense winter air easily overcome both the timing penalty and the slightly less energetic winter fuel blend. [1]

4. 🏆 Winter 91 (Absolute Best Performance)

• Peak Oxygen Mass: Freezing ambient temperatures provide the highest possible air density and maximum oxygen delivery to the engine.
• Maximum Spark Advance: Premium 91 octane allows the ECU to advance ignition timing to its absolute upper limit with zero threat of detonation.
• Maximum Output: This setup delivers the highest horsepower and torque your Mustang can physically produce on pump gas.