The ignition temperature point of gasoline (petrol) is 280 C Considering that the hottest sunny day on earth recorded was 134 degrees F (56.66 C) at Greenland Ranch, CA in July 1913. The highest temperature at Death Valley, CA (often thought of as the hottest place on Earth) was only 127 F (52.77 C) degrees in August 1993. Even allowing for reaching the boiling point of water 212F /100C The combustion temperature of gasoline is still low enough to not burst into flames via the sun. A match head burns at 3014.6 ºF (1657 C). Even solar water heaters can not push water over the boiling point, and they are designed for maximum absorption of solar radiation for heating. That ranges from temperatures of 160 to 350 F (71.11 to 176.66 C) Before you get excited by that high number there, that is for a collector ringed with mirrors that reflect and magnify solar heat around the tube. the lower number is for the simple black box with tube designs that does not magnify or track after the sun. So a gasoline/petrol tank does not need to be insulated or otherwise protected from the sun. There is no way it can reach the temperature of combustion of the gas/petrol even in sunny Death Valley California. Now it is well known that the vapors that escape from the liquid can be extremely touchy to sparks, this is why one is not supposed to smoke or discharge electrostatic energy when opening or filling a tank. There have been a few cases where static electricity has sparked a gas tank fire, igniting the fumes, not the gasoline itself.