Very little. While it is true that gasoline expands as it gets hotter (Reducing the energy content in a given volume). The expansion is only about 1% for every 15 degrees F. Moreover storage tanks at gasoline stations are buried several feet underground, helping to insulate fuel and keep the temperature relatively constant. The benefit: If any of filling up in the morning versus the evening would be hard to notice

Gasoline does expand and contract a little depending on its temperature. When gasoline rises from 60 to 75 degrees F, for instance, it increases in volume by 1 percent while the energy content remains the same.

But filling stations typically store their gasoline in underground tanks, where the temperature variation during the day is much less than in the air above. In consequence is that the temperature of the gasoline coming out of the fuel nozzle varies very little, if at all, during any 24-hour stretch at any particular station.

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