Am I safe to not fill up anymore gas even though the fuel indicator is right on "E"? [closed]

Question

I was driving my rental Toyota Corolla on the freeway this evening, when the low fuel light turned on. According to a source, "after the gas light comes on, Muñoz says it’s safe to drive about 20 to 30 miles in a smaller vehicle or up to 50 miles in a larger vehicle."

So let's say the Corolla had about 20 miles left in the tank. After the low fuel light turned on, I estimate I drove about 7 miles mostly on the freeway before stopping. At this point the fuel indicator was not touching the "E" line yet. Then I went to a gas station and added 0.8 gallons of gas (because I'm returning the car tomorrow and I already paid the car rental agency for a tank of fuel, meaning that I can return the car empty). I'm not sure what year this Corolla is, but apparently Corollas get about 30 mpg in the city. Since I added 0.8 gallons, that means I added about 24 more miles. So 20-7+24 = about 37 miles in the tank.

After adding the 0.8 gallons, I thought the fuel indicator would move up slightly, but it did not, and the low fuel light stayed on. Then I drove about 10 miles mostly on the freeway and stopped at another gas station. At this point, the fuel indicator was touching the edge of the "E" line. I added 0.75 gallons of gas (about 22 miles). So the car should have had 37-10+22 = about 49 miles in the tank. Again, the fuel indicator did not move up at all, and the low fuel light was still on. Then I drove another 3 miles mostly on the freeway.

So based on my very conservative calculations, the car should have about 46 miles in the tank now, but the fuel indicator is now fully overlapping the "E" line.

Tomorrow I am going to squeeze in one more museum (2 miles away) and then return the car (3 miles from the museum). I am concerned that even though I added about 1.5 gallons of gas, the fuel indicator is now fully overlapping the "E" line. Am I safe to go without adding more gas tomorrow (I've been trying to save my company money since I chose the "don't need to refuel before returning" gas option)? I definitely would prefer not to spend 15-20 minutes detouring for a gas station, since I'll be very pressed for time tomorrow.

Answer 1

Fuel gauges are electromechanical and prone to friction (though they don't normally stick as badly as I've had in my old van). They're certainly not precision instruments. The low fuel light seems to latch on until you've put more in, at least in some cars I've owned, probably to avoid it going on and off as the slope of the road changes.

But you'll get worse than the 30mpg you quote for two main reasons:

• published figures are almost impossible to reach in reality.
• most of your driving is from cold on these short journeys, and cold engines are less efficient

Fuel is far cheaper than the likely costs of running out - you're likely to be charged for the car having to be dealt with, let alone if you miss a flight (a common reason to be hiring a car). I wouldn't chance it, and fuel here costs about twice as much as in the US.