oil light on 2005 neon

I've seen high mileage engines do that. The rpms go down so does the oil pressure. When the rpms go up so does the oil pressure. Some generic specs say, 20--30 psi oil pressure at idle. 40--60 psi at cruising speed. You could try an analog pressure gage that screws in where the oil pressure sending unit is located, to check actual oil pressure. Some vehicles the oil lite won't come on unless oil pressure gets below 10 psi. These figures are just generic.