First of, do not use Restore Oil Additive in your engine ! My 95 Ford F150 302 V8 has 207000 miles on it and has 55-60lbs oil pressure always. I decided to try this additive so I did an oil change with Castrol High Mileage oil and a Purolator filter. I added the 8 cylinder formula of Restore and proceeded to drive my truck. I got 48 miles into the oil change on interstate 64 when all of a sudden my oil pressure guage started to fluctuate and the needle was bouncing.
I slowed down and my oil pressure went to zero. I shifted into neutral and immediately shut off the engine. I coasted to the side and stopped. I let the engine sit for about 5 minutes and tried to restart it. It fired right up and the oil pressure came back. I started driving again and got about a mile before it happened again. Luckily I got off the interstate next to the exit for Walmart. I walked a mile and a half to Walmart and bought a Fram filter ( they didn't have a Purolator to fit my truck) 5 quarts of Castrol High Mileage oil and a drip pan.
I drained the oil completely , changed the filter and refired my engine. It held 60 lbs of pressure and I continued my trip of another 85 miles. No further problems with oil pressure. I made the return trip of 110 miles and had no problems with the oil pressure. I think the additive I put in the oil caused this problem and would caution anyone contemplating using this additive to rethink it. If I hadn't paid attention to my oil pressure guage , I would have lost my engine for sure with the complete loss of oil pressure.