Why is the oil light coming on in my 1999 Chevy Cavalier when I stop at a redlight and engine warm full?

The oil light coming on in your 1999 Chevy Cavalier only when stopped at a red light with a warm engine points strongly towards low oil pressure. While it *could* be other things (we'll get to those), low oil pressure is the most likely culprit given the specific circumstances.

Here's why:

* Oil pump: The oil pump is driven by the engine. When the engine is idling (stopped at a red light), it's turning slower. A weak or failing oil pump might not be able to maintain sufficient pressure at idle, especially when the oil is already warm and less viscous. This is exacerbated by engine wear and tear which can lead to clearances that affect oil pressure, and it's even more problematic in a 24-year-old car.

* Low oil level: Even if your oil level appears full on the dipstick, it might actually be low. The dipstick only measures the *amount* of oil, not the *pressure*. A low level could lead to inadequate lubrication and low oil pressure, particularly at idle.

* Oil viscosity: Using the wrong viscosity oil (too thin for the temperature) can contribute to low oil pressure, especially when warm.

* Worn engine bearings: If your engine bearings are significantly worn, they might allow excessive oil leakage, reducing pressure. This is a more serious issue indicating significant engine wear.

* Clogged oil pickup tube: An obstructed oil pickup tube can restrict the flow of oil to the pump, resulting in low pressure.

* Faulty oil pressure sensor: While less likely given the other symptoms, a faulty sensor *could* be giving a false reading. However, if it were consistently malfunctioning it might also trigger a light even when driving.

What you MUST do:

1. Do NOT drive the car. Continuing to drive with a low oil pressure warning light can cause catastrophic engine damage.

2. Check your oil level immediately. Make sure it's at the correct level on the dipstick *when the engine is cold*.

3. Check your oil pressure gauge (if equipped). If you have one, this will confirm your suspicions.

4. Have your car towed to a mechanic. This isn't a DIY fix. The underlying problem needs professional diagnosis and repair to prevent potentially expensive engine damage.

Ignoring this warning light could lead to a seized engine, which would be a very costly repair or even a total engine replacement. Get it checked out as soon as possible.