My 1997 Miata has an oil pressure guage at the top of the instrument cluster and it pops right up when the engine is started. That seems to be a good thing, but is it truly showing pressure or is it just showing that there is oil inside the motor? Somewhere I have read that it is just another version of an "idiot light" and should not be trusted! Anyone with definetive info on this please chime in. If it is and idiot light/guage, can it be changed out to a true pressure gauge and hard hard is that to do to someone not all that task-friendly? Thanks