Engine Mechanical problem
1999 Pontiac Sunfire 4 cyl Front Wheel Drive Automatic 125000 miles

The 1999 Sunfire (125000 miles) is a 2nd car, used only to run errands and shop. On short trips (less then 20 miles round trip) its fine. On longer trips (20+ miles, especially in warm weather) when idling at stoplights the oil light will come on. Oil light will go off by giving it more gas while stopped at the light.

Is it the oil pump?

Or a low idle? Though no other problems with current idle speed.

Or an overheating problem, does the sensor also detect oil that's too hot? H2O temperature never is more than halfway up the gauge when this happens.

Idle speed seems to be the cheapest thing to check first.