# #1312: How far can you go with the (E) light on?

Your solution to finding out what your “empty gas tank” warning light (which, by design, is devious – you CAN’T be empty, you’re still going) is to use the trip odometer.

Years ago, when my 1987 Jeep YJ Wrangler was newish, I determined that the gas gauge was really off. I mean it would hover around the top 1/4 of the range for a hundred miles, then meander down to the 1/2 point leisurely, then over the next 50 miles dive down to E like an Olympic high diver scoring the gold. I knew I had to find a new way to guesstimate my gas consumption.

Over the course of the first few months with the Jeep – the honeymoon – I got increasingly close to E (there was no light on this dinosaur), then filled up, and noted the amount that I filled up. I recorded my mileage and gas consumption, calculating my (dismal) MPG, so I knew how far I’d gone between fill ups. I knew the capacity of the 20 gallon gas tank. When I filled up to the tune of 19.0 or 19.5 gallons, a few weeks of routine driving, I knew how far 19 gallons would take me. It didn’t take too long to determine that around 400 miles since the last fill up, I was down to a gallon or so of gas, which in the Jeep would get me about 100 yards further.

I do the same with my Acura TSX (Honda CL9 Accord). The handy dandy (E) comes on well before the gas is really gone. The tank capacity is 17.1 gallons, as per the owner’s manual and other documentation. By filling up right when the (E) light comes on solid (not peek-a-boo, now you see it now you don’t), I’ve determined it comes on at about 13.8 gallons. Using my average mileage (you can use the upload spreadsheet from FuelEconomy.gov that lets you track your mileage), 27.1 MPG, I know … the remainder will safely take me at least 75 miles before I need to pull into the nearest gas station.

It’s easy. Just fill up when the E light comes on. Note the gallons you put in (don’t pop-pop-pop try to put a few ounces in when it cuts off). Subtract that from your car’s stated capacity. Multiple the remainder by your worst possible mileage. There … that’s how far you got to go. Just set the trip odometer when the light starts coming on, start making plans to buy gas. Depending upon your routine driving habits (short trips, or a long daily commute), you can figure out how urgent your need to fill up is.

I’d be a little concerned about running the tank empty on newer cars. In many cases the fuel pump is in the tank and as silly as it sounds ( to me ) the fuel is the coolant for the pump. I’ve had customers whom actually burned out the pump by running out. How many times they tried to start with no fuel I’m sure was a factor. In any case, if the Subaru has an in tank pump I wouldn’t risk it.

Knowing how far you go between fuelings is how to work your vehicle anyway…
BUT NOT DOWN TO NEAR EMPTY !
It takes the exact same amount of weekly cash to drive with a tank near full.
My son would argue ''it costs more to fill it up."
To which I retort “just ONCE, does it cost any more”.
he looks confused ;( …
till I show him how the exact same amout of weekly gas money will go the exact same distance each week if only he not wait for empty…just put in those same dollars each week.

Plus I showed him an electric fuel pump/sender so he could see the truth…then he understood.
It costs a helluva lot more to replace a pump than to fill up ONCE.

You’re a man totally confident in the world around you. Being suspicious all the ime, I would fill up before the one quarter mark and half in areas I didn’t know and not worry about where the next gas station is.

The idea of the low fuel light is to get gas at the next opportunity when the light goes on. Even in the same model car, the distance varies from car to car. Also if you are driving on a highway or in city stop and go, the distance varies.

No one can tell you how many miles are left after the low fuel light goes on. If you really want to know put a full 2 gallon gas container in the back of your car and run it until it stops. Then you’ll know. This is not really a good idea, as running out of gas can harm your fuel pump and clog your fuel filter. But, if you really must know.

I should be clear, I don’t espouse running to empty or near empty. I agree, it can’t be good for the fuel pump. Or your pocketbook – you end up being forced to buy gas nearby, which may be high-priced.

My point is that when you see the (E) light, don’t freak out and scream and dash to the nearest station. Knowing if you have roughly (I’ll say that again,… roughly) 25, or 50, or 75 miles left before you get even close to the last gallon of gas in your tank lets you make an INFORMED and REASONED decision about where to buy. (And with mobile apps like Gas Buddy, you can look for the best price nearby.)

As I believe I inferred, mileage may vary. Knowing your AVERAGE mileage allows you to make a fair estimate of how far you can go with the volume of gas you now KNOW is in your tank (having determined when the light goes on).

I posted as an argument to the caller who would abuse his new car by running it empty to see how far he’d get. He doesn’t have to! Just figuring out the remainder in the tank when the light goes on and doing simple, 5th grade math, will suffice.

To answer his question, “Is it hurting the car,” I’d answer YES!! Of course it hurts the car to do something you shouldn’t (run it on empty), so … don’t … do … that.

Look, it’s common knowledge that there is a “reserve” built into virtually every car out there. It’s probably a good idea, and it really isn’t dishonest, as all parties are somewhat aware of the fact.

What rubs me the wrong way are the games Ford plays with their “Distance to Empty” display on my mom’s 2010 Fusion hybrid. It starts out (above half-tank) with what seems to be an honest appraisal of range to “tanks dry”–no reserve added.

Then, between 1/2 and 1/4 tank, the DTE starts “stealing away” a reserve, a mile or so at a time, until a ~35 mi reserve is accumulated. It seems to be deliberately done incrementally, so that the driver would be unaware, unless he was, say, monitoring range vs. distance to a fuel stop/trip end (which is what clued me in).

It’s damn frustrating, telling the passengers “we won’t need to make a fuel stop” (based on the initial range calculations), only to see the “cushion” melt like snow in the sun! (And yes, I was able to rule out the possibility of hills or something causing excess fuel burn: the portion of trip from 1/2 to 1/4 tank was actually some of the thriftiest driving of the trip.)

The only reason I can see for this is Ford wants to “have it both ways”: a brag-worthy DTE displayed at fill-up, AND a comfortable reserve at E. The dishonesty bothers me: the driver in command of the vehicle needs various data to conduct the trip safely and efficiently, and the thought of the car’s computer feeding the driver distorted data reminds me of (a much more benign version of) HAL 9000.

I don’t see that any damage could be done by running the tank down just once. There might be slight additional brush or bearing wear on the pump but it’s the drivers who do that on a regular basis who are taking their chances.

All vehicles seem to have trip odometers these days and zeroing the trip meter at each fill up and refilling when the mileage reaches what would realistically be 60% of the range of a full tank keeps my EKG on track. I ran out of gas once and it was no fun.

It runs until the gas is gone.

(grin)

The gauge dives down to empty fast because the float arm travels in an arc, not a straight line.

Most travel in a straight line up and down the side of the pump tube.