1997 Ford Taurus oil light

My oil light is coming on when I am stopped at a light or other short term stop while in drive. Once I accelerate, the light goes off. When in park or neutral the light is off. A moth ago, I had no heat and no anti-freeze. I filled the anti-freeze and replaced the thermostat, which solved the problem. I change the oil and poured an oil treatement and sealer in the oil since the machanic who changed the oil said he thought there was anti-freeze in the oil. My check engine light was on prior to an oil change. Since the oil sealer was added the check engine light is off. But now the oil light is on. I check the oil regularly. No sgns of water or anti-freeze in on the dip stick. No signs of water or anti-freeze leaking out of the tailpipe. No oil smoke out of the tailpipe. There does seem to be a burnt smell after long drives when I turn the car off. By long drive, I mean 30 miles of highway speed on to work. Any help on what the problem might be, would be appreciated.