So, many years ago, Amanda and I got a new car. The first thing we did was to switch get rid of my old Rodeo, and I took her old Subaru sedan, and she drove the new Forrester. So, thereafter I drove her old car, and she drove our new car.
One day I was on my way back home, and I noticed that the gas gauge needle was on E, but the Empty Tank Warning Light was not on. So I figured I’d get gas at the place near home, rather than stopping sooner.
Driving down the highway, the car sputtered and stopped working. I got it over to the side of the highway. Knowing that it was not out of gas, because the warning light was not on, I opted to be towed to the station, just a half mile away (I was almost home!) rather than to try fixing it on the road.
By the end of the day, I learned that the problem with the car, the reason it stopped on the highway, was this: Out of gas!
Later, I mentioned to Amanda that her former car’s gas tank warning light didn’t seem to be working any more, and I thought there was 20 miles or so before it went empty! Her response: “It has never worked, since I bought the car. You are thinking of the other car, dummy!”
Well, she didn’t say “dummy” but she should have. And, the answer to the question at the top of this post, with respect to that particular car, is: Undefined.
Much more recently, we were driving our Prius back from a visit up north. We passed the gas statin in Rice, but shouldn’t have, because we were almost out. Coming down into Saint Cloud, the warning light came on. Then, we hit a major traffic jam. There was no way we were going to make it to the gas station.
But, we were going down hill in stop and go traffic in a Prius. So, we switched to “Battery Mode” and stopped using gas for the next 10 minutes. No problem.
The point is, the answer to the question is necessarily imprecise. The best strategy is to avoid letting the light go on. Which, by the way, brings up an important digression into another myth: How empty should you let your car’s gas tank get?
It has long been thought that letting your car get too empty is a bad thing. For modern cars, this is a myth. It may always have been a myth. But today, all the reasons ever cited to avoid this are wrong except two. So, the rule that you should fill your tank when it is one quarter full is incorrect, ignore that. It doesn’t matter when you fill your tank.
But, this part is true: You don’t want your car to run out of gas. Why? Well because then it won’t go! Obviously. But there is another reason. It is actually possible that parts of your system, such as the catalytic converter, will be damaged or stressed by the process of zero-fuel-engine-stoppage. I’m not sure how that happens, but it can happen.
Also, it is a myth that you should not fill the tank on a hot day. You should, actually, never “top off” the tank. Just fill it until the hose clicks you off and leave it at that. Modern cars are designed to handle gas expansion, modern cars in combination with modern gas, are designed to handle moisture in the tank, etc. etc. These various rules about gas are either no longer valid because of changes in technology, or were never true, and merely part of Car Lore.
Anyway, back to the point. Your Mechanic web site has put together a table showing how long you have to drive, estimated and on average, and depending, for each of several makes and models of car, when the emergency fuel light goes on.
I’ve pasted it below, but first, I am reminded of a second myth. Sometimes the out of fuel light is in the form of a tiny gas tank, with the hose on one side. It is said that the side that has the hose on it (see illustration above) indicates which side of the car your filler hole is, which is handy if you are driving a borrowed or rented car.
It doesn’t. Well, maybe about half the time it does, but no, this is not a thing.
Here’s the chart: