Dear Car Talk

When the oil light is on, is the oil pressure low or is the oil level low? — Bob



Yes

Unless otherwise noted, a red light that says “OIL” on the dashboard means your oil pressure is dangerously low. Of course, the pressure could be low because you don’t have enough oil in there.

But oil pressure can also be low because your oil pump is failing, because your engine bearings are all worn out and they’re too loose to maintain pressure or for a number of other reasons — none of which are good news.

So when you see a red light that just says “OIL,” that means your pressure is low, and you’ll want to pull over and shut off the engine as quickly as it’s safe to do so

Sometimes you’ll see the oil light flicker, especially when you’re at idle — like at a traffic light. That’s when oil pressure is at its lowest anyway. It’s a sign that you’re on the verge of having a serious problem.

At that point, we usually recommend a mixture of 90 weight gear oil, sawdust and bananas in the crank case. Or whatever tropical fruits happen to be in season.

There are a few cases where the oil light comes on simply because the oil pressure sensor is bad. That’s a lucky break. But, generally speaking, seeing the oil light come on while you’re driving is bad news. And it’s a light you never want to ignore.

On the other hand, lots of newer cars also come with an oil level light, which is different. That’s not an emergency warning light. It’s more of a maintenance reminder light. The oil level light is designed to eliminate your need to check your oil with a dipstick.

Checking the oil used to be a regular chore for car owners. But most people don’t want to do anything other than start the car and drive these days. And based on the rush to self-driving cars, it’s clear we don’t even want to do that much anymore.

Over the years, we’ve made clear to car makers that rolling down our own windows or taking the key out of our pockets is way too much trouble, so many of them have eliminated the dipstick and replaced it with a sensor.

If your car has an oil level light, and it comes on, that’s just a sign that you need more oil. It’s usually not an emergency. That light will normally come on when you’re down a quart.

While it’s not ideal to drive around down a quart of oil, you can certainly drive until you can get to a gas station or a Cheapo- Mart where you can buy a quart. You shouldn’t do any lasting damage if you take care of it in a timely manner.

If the light doesn’t turn off after you add a quart, then drive it to your repair shop, because you may have a leak or some other problem.

Resist the urge to add a second, third or fourth quart, so you don’t overfill the crankcase and do more damage.

To sum up, as much as we hate to do this to you, Bob, we’re going to send you to your owner’s manual. Look up “oil light” in the index at the back of the book.

If you have two different oil lights, you’ll need to know that. And you’ll need to know how to distinguish between them so when one of them comes on, you’ll know if it’s time to mosey on over to your gas station or to your new car dealer’s showroom.