Pontiac Repair: Grand AM Quad 4 2.3 liter oil pressure drop, fuel pressure regulator, pressure gauge

Question
dear wayne:

recently i dicovered a dramatic oil pressure drop while traveling for about 2 hours. (150 miles). when i started the trip, i filled up the oil level to "full". i used 5w40 engine oil. during the trip the pressure gauge slowly went down to almost 0, after i had already driven about 100 miles. i usually drive in town, no long trips. then when i stopped the engine for about 5 minutes, the pressure came back into the normal area (above the first white line). after a while it went down to 0 again. the mechanics i asked say that they cannot hear any rattling from the connecting rod bear rings, what is usually a reason for pressure lost. they also told me, to better use 10w40 on an old engine like mine (it's a 1988 quad 4 with about 120000 miles on it. before i have changed the oil, i had used 10w40 without any trouble for 2 years. i have used the 5w40 during the winter now, where i had the heater running all the time. on this trip now it was the first time i used the ac. so the engine could heat up more. the oil also smells like gas a lot and is pretty dark after only about 1000 miles yet. what would you recomment?

thanks,
andy

Answer
Hi, what I would do is to check out the gas smell in the oil. This can cause the oil to become to thin, and cause the oil pressure to drop. Have the fuel pressure regulator checked. After get this taking care of, then I would go  back to the 10w40 oil.