I guess we're changing the subject from oil pressure to alternator ...
There are three small diodes inside the alternator besides the six power diodes.
If one or two diodes are defective from these smaller ones the self excitation
will be inadequate, and causes the glowing of the charging fault indicator bulb.
The glow depends on the alternator load: turning on more electrical consumers
will increase the glow intensity (you can check this at running engine).
The alternator is still cabaple to charge, but it's efficency is slightly reduced.
In this case the higher wattage bulb(s) won't solve the problem.
(If all three diodes are dead, that's a strange situation, because the charging fault
bulb will lit, despite of the alternator is still able to provide charging, of course the
efficiency loss will be higher.)