well yeah it's the tree that hid the forest in my head .... i imagined that the magnets could have an action on the whole material ... the beam in the eye ...
Well now it seems to me much more obvious that a magnetic field, applying to anything, will have an effect .... on the electron / nucleus which have a charge ...
On the other hand, quantifying the effects is the question, the enigma ... which we will try to solve here for petroleum products ...
The magnetic effects are very visible on ferromagnetic materials, kind 300 to 2000 times more important than on diamagnetic or paramagnetic .....
For "metallic" deposits in the injection pump. You can also try to trap them by sticking a strong magnet on the outer casing of the pump (the field lines pass on the other side of the casing if in aluminum), where the wall is thinnest and at the lowest point if possible.
the most known decanter on a car is ... The reservoir, this is where it settles first;
then you have: the diesel filter: it is at the bottom that there is precisely, provided at the bottom of the decantation, a water detector, because the water is heavier than diesel (= oil).
The problem with the tank is that it is most often made of steel, so a magnet placed or fixed to the bottom will see its fields channeled almost completely on its walls and will therefore only weakly attract the magnetic particles suspended in the fuel. . In addition to each turning / braking, the fuel moving in the tank, will recirculate what had been deposited with difficulty ... It would require a plastic tank for example, with a low point not too agitated during vehicle accelerations ...