Running on empty

[Nick R]

How many of you have continued to drive after your car is telling you that there is no fuel left? I usually let it get down to like 15mte before I fill, been down to 0 once or twice, but only briefly, Well, I'm at class, my milometer is telling me I have 8 miles to empty. I have 30 to drive. I think I can make it. Last time it said 0 I ended up having a full gallon of fuel left.

The reason is gas around my school is about 25c a gallon more than near my house.

 

[Quest]

Ever since I began working on EFI cars with electrical fuel pumps in-tank, I've been telling all vehicle owners not to run the tank til bone-dry, for the sake of not burning out the commutator brushes and bushings inside the pump (even the vanes for certain pump brands/designs).

Yes, there are some posters in the past where they said that they could get their car back into action by fuelling it up after running (more like stalling) their vehicles on the roadside by running their tank bone dry.

Truth is: these fuel pumps rely on fuel acting as a very light lubricant (on vanes, bushings, etc.) and also to keep the commutator brushes working properly. You may claim luck when you get it back from dry state but chances are, your pump has already suffered greatly as a result and it will fail prematurely, when? maybe in a matter of months, or days?

**observations: none of my owned vehicles (most reaped up to over 200,000kms to clock, fully maintained by yours-truly) ever need a fuel pump replacement. But then again: I never run my tank bone dry.

Q.

 

[KrisZ]

The computer is just being conservative, you're not empty, my Mazda does the same thing. When the low fuel light comes on, the display usually shows 30 miles to empty, depending on my fuel economy on that tank.

My tank is 14.5 gallons, when the low light comes on and I fill up, it takes about 12 gallons, so I have about 2.5 gallons still left in the tank.

On many road trips I went about 100 kilometers (62 miles) after the computer told me I had zero miles left and it still took about 13 gallons to fill up.

Learn your car, see how much it takes to fill up vs the total capacity of your gas tank, you want to keep 1.5-2 gallon fuel reserve.

 

[mongo161]

I just drove from Orlando, FL back home to Coney Island. For each of my fill ups, I let the gas tank run down to very low. Each time I filled up, I added 17 gallons of gas and the tank holds 18 gallons. Since I was doing high speed driving from FL to NYC, I wanted to burn up as much of the old sediment that accumulates in the tank. I added 3-4 ounces of TC-W3 and an equal amount of Chevron Techron Fuel System Cleaner to each tank fill.

BTW...I did the same procedure on my trip down to Orlando from NYC. I figured with a hot engine, running fast and at high speeds for 1,400 miles straight through, any sediment that is in the tank will burn off clean with the TC-W3 and Chevron Fuel System Cleaner.

Good to be home but I really enjoyed Florida for a month.

 

[Quattro Pete]

Originally Posted By: Nick R
Last time it said 0 I ended up having a full gallon of fuel left.

How would you know that you had a gallon left? I'm guessing you calculated this based on how much gasoline you were able to put in at that point and subtracting it from the total tank capacity - just keep in mind these total tank capacities are sometimes inaccurate. So are some gas pumps.

In any case, the way these "MTE" computers are calibrated varies greatly from car to car, mfg to mfg, although typically there will be a small amount of buffer (safety margin) left, even if the value does go down to "0". I did go down to "0" on my 530i once and drove another 3-4 miles past that, at which point I was able to put in 18.7 gallons, even though my tank is only supposed to hold 18.5 gallons. But typically I try to fill up right after the light comes on, at which point the range still shows about 50-55 miles left.

The "MTE" on the wife's C300 is fairly useless on the other hand. Once it gets down to about 25 miles, it stops displaying the miles and just shows a big honking gas pump icon. And there is plenty of gas still left in the tank at that point, it seems.

What the previous poster stated about your fuel pump being cooled by gasoline is also valid, from what I've read.

 

[MNgopher]

This topic comes up from time to time, with stong opinions on either side.

In my case, I routinely drive until the low fuel light turns on in all my vehicles. Each vehicle has a different amount of fuel in the tank when the lamp turns on (in my fleet now, the Jeep still has about 3.5 gallons (of a 20 gallon tank), the Explorer is tough to say becuase I rountinely get about 21 gallons into a 20 gallon tank (and I've gotten over 23 before), and the F150 still has 3 gallons in a 30 gallon tank).

Despite the abundant advice that this is hard on fuel pumps, etc, I've never had to replace a fuel pump in a vehicle. This is over 6 cars/trucks representing 915,000+ miles.

 

[NateDN10]

You could put a gallon of gas in near school and fill the rest of the way once you get home. That way you're only wasting a quarter, and you know you won't run out of gas.

 

[Quattro Pete]

Originally Posted By: MNgopher
Despite the abundant advice that this is hard on fuel pumps, etc, I've never had to replace a fuel pump in a vehicle. This is over 6 cars/trucks representing 915,000+ miles.

I think the fuel pump cooling becomes an issue if you run it bone dry, not if you just wait until the fuel light comes on, at which point like you said, a typical car will have 2-3 gallons of fuel left, which is probably still plenty for proper fuel pump cooling.

 

[Pop_Rivit]

Originally Posted By: Nick R
How many of you have continued to drive after your car is telling you that there is no fuel left?


Never.

It's rare that I have less than half a tank in any of my vehicles. Should I need to "get in and go" for some reason I always want enough to get me down the road quite a distance.

With a little planning you wouldn't be in a situation where you have to wonder if you can go 30 miles when your computer tells you there's only 8 miles remaining. Get out of bed a little earlier and fill up on the way to school.

 

[IndyIan]

Originally Posted By: NateDN10
You could put a gallon of gas in near school and fill the rest of the way once you get home. That way you're only wasting a quarter, and you know you won't run out of gas.

+1 It sounds like you've only really got a 8 mile estimated buffer, trying to do another 30 miles on the hypothetical gallon... I'd rather pay $2.50 more than run out of gas.

 

[BigBuck]

I fill up at a quarter tank. If I were you I wouldn't put myself in the position where I would be low near school. Just fill up before class. Or the day before you usually would. Save yourself the trouble

 

[addyguy]

A few times I've ru my vehicles down to where the fuel light comes on, but I really don't like to.

You never know what will happen, and having absolutely no gas in a small emergency is really silly. I usually try to fill between 1/4 and 1/8 of a tank left.

I don't actually fret to much about gas prices, or desparately try to pay as little as possible - I need gas, I get it. Some days I get lucky with prices, other times, I don't.

Put in even 1 gallon of gas, and then fill near your haouse - you'll still save a chunk.....

 

[sciphi]

The gas gauge on the Buick will rest on E when 5 gallons remain. So it will freak everybody out, yet the car still can travel an hour or so. I let the tank get low every week since it's better for fuel economy, and gas is convenient along my common driving routes.

 

[rslifkin]

My low fuel light comes on with about 3 gallons remaining. I've hit that a few times on long trips when I know I'll get in with 2.5 or so left in the 23 gallon tank. I ran it down to 1 gallon remaining once, and make a point not to run it low often. Usually, I fill up with 5 - 8 gallons left in the tank.

 

[Astro14]

+1 on the fuel pump cooling.

In direct answer: Never - I used to work in NYC. I always had a reserve in case the "unexpected" 2 hours traffic jam materialized...on many NYC streets/highways there is NO place to pull over.

I simply had to plan better and purchase fuel where it was cheap in anticipation of the upcoming requirement...

This is true for airplanes as well...I always planned better than to have to keep "driving" when the gauge showed empty...

 

[buickman50401]

Originally Posted By: Quattro Pete
Originally Posted By: MNgopher
Despite the abundant advice that this is hard on fuel pumps, etc, I've never had to replace a fuel pump in a vehicle. This is over 6 cars/trucks representing 915,000+ miles.

I think the fuel pump cooling becomes an issue if you run it bone dry, not if you just wait until the fuel light comes on, at which point like you said, a typical car will have 2-3 gallons of fuel left, which is probably still plenty for proper fuel pump cooling.

I've seen in more than one GM manual (can't remember if its in my Buick's manual, but I do remember it being in my 98 Grand Am's) the wording to the effect of "Do not routinely drive your vehicle with less than 1/4 of a tank of fuel. The fuel pump relies on gasoline for cooling. Routinely driving your vehicle with less than 1/4 of a tank will drastically reduce your fuel pumps life."

 

[mongo161]

"Routinely driving your vehicle with less than 1/4 of a tank will drastically reduce your fuel pumps life." [/quote]

Routinely....is the key to this procedure. I don't drive down to 1 or 2 gallons of gasoline remaining in the tank on a routine basis. However, if I'm making a long high speed trip with minimal stops, I like to get out as much of the old fuel and sediment that lays on bottom of the tank by diluting it with fresh gasoline and TC-W3/Chevron Techron Fuel system cleaner.

IMO...The TC-W3 adds plenty of Lube to the Upper Cylinder, Fuel Pump and Fuel System while the Chevron Techron Fuel System cleaner helps dissolve any deposits or build up in the fuel line, fuel pump and gas tank.


After my long trip, I now feel confident that most of the old build up has be "blown out" with the 70 to 85 MPH driving on I-95 from Florida to NYC along with any residual "winter blend" gasoline. The added benefit was the use of Chevron Gasoline while on my trip. I bought and used this gasoline wherever I could find it on my journey.

IMO...this is the best way to purge the fuel system of any impurities that build up over time.

 

[kkreit01]

I've never ran out of gas, and typically don't come close. I came within 8 mi left on my MKZ -- but that was on purpose -- just to see if 0 really means "empty". It was in town, and had several stations to chose from. I found out when it says 0 miles left, it does mean 0. I only had about 1/2 gallon left at 8 miles to empty.

 

[Quattro Pete]

Originally Posted By: buickman50401
"Do not routinely drive your vehicle with less than 1/4 of a tank of fuel. The fuel pump relies on gasoline for cooling. Routinely driving your vehicle with less than 1/4 of a tank will drastically reduce your fuel pumps life."

So, the owner's manual for my 530i says the following:

Quote:
Please refuel early, since driving
to the last drop of fuel can result in
damage to the engine and/or catalytic
converter.

I've heard this before, too, but can someone refresh my memory: why would this damage the cat?

 

[IndyIan]

Maybe running lean will overheat the cat? My Neon ran for quite a while on "fumes" when I ran out of gas(gauge hung up at 1/8th). Usually cats get killed from running rich and overheat from burning too much fuel.