Your fuel is just not hot enough, even in the hot summer, to call hot. Sure, in theory, if things are running cooler for a fuel engine, you are getting more power, but the big question is how much cooler the fuel needs to be to make extra. But for other things, such as the engine itself, if it is 10% cooler, you can extract more Power out of it.

Mclaren is appealing about the fuel issue for the last race in F1. Personally I do not think it is going to make Lewis to win the Driver Champion, but they do not lose anything from the appeal.