The oil pressure sensor is located at the rear of the engine here are diagrams BELOW so you can see the location.
First be aware that gauges are notoriously inaccurate. They're best used to let you know when something is not normal, but that's it. If this is something new that you haven't seen before, have the actual oil pressure tested with a mechanical gauge.
If I were to see this for the first time in your car, I'd say this is perfectly normal. (Not dropping to 0 psi, obviously), but there's nothing wrong with 30 psi. Most cars today use very thin oil for lower internal friction and better fuel mileage. Along with that, any oil will get thinner when it gets hot. That lets it run out of the bearings easier. You need higher volume to maintain a higher pressure, and that's what you get when you raise engine speed. The oil pump runs faster and is able to supply enough oil to make up for that which is running through the bearings faster.
Dropping to 0 psi momentarily could be explained by a bad spot in the old sending unit, and in fact, we used to see quite a few in the '90s that dropped a real lot at idle speeds. The actual oil pressure probably dropped five or ten pounds, but the gauge implied it dropped a lot more.
Worn engine bearings will cause low oil pressure too, but that typically only lasts a few hundred miles, then things get much worse real fast. If you've been changing the oil somewhat regularly, you don't really have enough miles to have worn bearings yet. Other causes include debris blocking the oil pickup screen, debris holding the pressure relief valve open, and low oil level causing air to be drawn up. The oil pump can be worn too but I haven't heard of that being common on your engine. That wouldn't really be intermittent either. The pressure would always be lower than what you're normally used to seeing.
Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.
Images (Click to enlarge)
Monday, April 27th, 2015 AT 9:44 PM