Flammable liquids have two critical temperature factors:
A. Flash point is the lowest temp. at which the liquid will vaporize naturally and ignite when a flame is applied.
B. Auto ignition temp is the lowest temp at which the vapors will combine with free Oxygen in the atmosphere and spontaneously ignite without an outside ignition source.
For gasoline A is -45F and B is 950F
For No 1 diesel A is 150F And B is 450F
So diesel, in theory, has greater potential to vaporize, and auto-ignite if sprayed on a hot manifold.
As a fire investigator from '63 to '80, I had to argue pros and cons of keeping engines running while fueling in marinas
Shutting down won out, but more because of the potentail of errant spark in the gasoline engines causing ignition of fueling vapors.
Every boat fire I investigated was caused at start up after fueling gasoline engines.
NFPA and USCG are very emphatic on this issue, but get one of them aside over a beer
, and see what they say.
My figures I am recalling from memory, correct me if I am wrong.
PLease investigate for yourself, BUT run those blowers anyway.