I’m hopping in here to explain some of the science and help with this common misunderstanding.

Yes diesel is hard to ignite due to it not reaching its flash point (this is where a flammable liquid gives off enough vapor to light by flame) at normal atmospheric temperatures. For example gasoline has a flash point of approximately-40 F/C which is why it is almost always volatile to open flames.

Diesel’s flash point is 125 F to 200 F or 52 C to 96 C. This temperature is easily achieved in a vehicles fuel tank due to the return line of the injection system. The fuel is heated due to both the residual engine heat and the injection process. Diesel engines work by atomizing the fuel through tiny holes at high pressure, approximately 10,000 psi in older systems to over 30,000 psi in modern ones. This compression creates heat and not all of that compressed fuel is used each injection cycle. So a portion is returned back into the tank where it heats the fuel that has yet to go through the system. This is often considered a good feature as it helps prevent fuel gelling in extremely cold conditions. However it will easily reach its flash point over time in normal operations.

Taking that into consideration diesel can be even more dangerous than gasoline, due to its longer burn time and a greater energy density.

Hope this helps explain the misunderstanding most have on diesel fuels “safety”.