The ignition point temperature of Aluminium is well over a thousand degrees, in the confined space of a tank it isn’t going to matter what the engine is made of if temperatures have reached that point.An aluminum block diesel is going to be a major, major fire hazard on a tank in any event.
Aluminum is a severe fire hazard, especially if it spalls. A cast-iron block engine takes longer to burn if hit.
The ignition point temperature of Aluminium is well over a thousand degrees, in the confined space of a tank it isn’t going to matter what the engine is made of if temperatures have reached that point.