Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

1/4 tank of gas

Last night one of our local T.V. news outlets was reporting on the high cost of gas and the anchor added “And be sure to not let your tank drop below 1/4 full on a regular basis to prevent costly engine damage.” Can this be true? I can’t find anything like that in the owner’s manual(s).

In my opinion, this is another reasonable pieces of advice (protects you from running out of fuel, which can cause fuel pump problems) that has been inflated into something urgent, when it’s not.

Agreed. I’ve heard on older cars that running the tank dry can suck some sediments down into the system and clog the fuel filter, but I don’t see any immediate danger.

It doesn’t have a thing to do with engine damage so I don’t know where that came from.

But its still good advice as texases noted.

Running the tank really low can be bad for the fuel pump since the fuel helps keep it cool.

I heard a similar report and asked my mechanic about it. He said doing it often (going below 1/4) over time COULD cause damage to the fuel pump, and in certain cars running low or out of gas can cause sensors to send false info. to the computer.

The advice has everything to do with running out of gas.

The advice becomes neccessary during high price times because of the MIS-conception people have with having ,say, only ten bucks a week ( formerly five bucks ) to put gas in the tank.
—The misconception ?
The supposed extra money it takes to keep it full.
–the truth ?
That ‘‘extra’’ gets shelled out JUST ONCE. After which that same ‘ten bucks a week’ get put in to a mostly full tank.

Personally, I wouldn’t intentionally run my car with less than 1/4 of a tank of gas, simply because it doesn’t save any money, it may damage the fuel pump (unproven concept, but why take chances with an expensive repair job?), and–of course–it puts you in greater danger of running out of gas.

That being said, I am reminded of an old boss of mine who drove a Buick, circa 1988. Clearly, not an economical car. Whenever it was necessary for the 6 people in my office to go to a different location for a meeting, he would offer to drive. And–inevitably–he would stop for gas along the way and get $5.00 worth! As far as I know, he used to buy $5.00 worth of gas every day.

This was somebody who could have well afforded to fill his tank each time that he gassed up–after all, the peons whom he supervised could afford to fill their tanks, so surely he could with his substantially higher salary. As to why he did this, I once asked him and he gave some sort of convoluted (and essentially incomprehensible) answer about…“this way they can’t cheat me at the station”. (???)

Anyway, my point is that despite lots of other problems with that Buick–including transmission failure–and despite the fact that this guy’s gas gauge never read above 1/4, he never had to replace a fuel pump! Hence what I said about an unproven concept.

Some current speculation in the news was that due to the high price of gas, there may be more people who permit their tanks run too close to empty, adding to the risk of running out of fuel which then will certainly happen.

Your in-tank electric fuel pump is lubricated and cooled by the fuel running through it so as long as the engine is running normally, your fuel pump electric motor will be fine. These motors have a wound wire rotor and permanent magnet fields so only the rotor needs a flow of fuel to keep it cooled.

The TV talking head was likely parroting something that someone else told him/her without a true understanding of what was said. Engines are not damaged by lack of fuel but the fuel pump life might be slightly shortened during the process of running out of fuel before the engine finally stops due to lack of fuel and the ignition switch is finally turned off.

Always get your car advice from a news anchor. They’re experts in automobile service and repair.

This is a line being pushed to TV stations by AAA. A station here said the same thing. They’re using a little psychology. What really causes the damage is running out of fuel, because that harms fuel pumps. So in order to scare drivers in to not letting the needle sit on E for a long time hoping gas prices will drop, they nudge the “danger” mark up to 1/4 tank.

Someone told me years ago that it costs just as much to keep your gas tank empty as it does to keep it full.

The news media ALWAYS reports the truth, though usually hidden within lies, deception, and tomfoolery.

It would make sense then for the manufacture to deny warranty consideration for people who let their fuel fall below 1/4 tank and have the car towed in with a inoperative fuel pump (or worse). Why should a manufacture pay for a pump or engine damaged by something the customer did? Come to think of it I never have read in any owners manual where it states your fuel pump or engine will be damaged if the fuel falls below 1/4 tank. Just to be safe, if the car fails to start and you suspect it is the pump (or a damaged engine), make sure the tank is full when it gets towed in so as you will not be denied warranty (the mechanics also love it when the tank is full and they have to drop the tank to change the pump).It is common knowledge that the fuel level data is stored in the “computer” and can be retrived with a scanner so the Dealer knows if you have been driving around with the tank low.

This is piece of advice that was more useful 20 years ago. Today gas pumps have effective filters in the pump and on the hose to catch sediment that is pulled up from the storage tank(s) at the station. Modern gas has alcohol in it which reduces water settling out in the gas too.

Therefore it is rare to have a lot of water and dirt sitting in the bottom of the fuel tank of your car. Still, the folks who never fill up and run around on 1/4 or lower all the time will have more fuel pump burnouts as the fuel in the tank helps cool the fuel pump. More gas in the tank is more cooling for the fuel pump.

These motors have a wound wire rotor and permanent magnet fields so only the rotor needs a flow of fuel to keep it cooled.

Almost all current in-tank gasoline fuel pumps are a gerotor design. Cooling the motor is one issue. The pump also requires fuel as a lubricant for the pump rotors. By nature of the design, the rotors are subjected to an imbalanced force between the high and low pressure sides that causes the rotors to be pushed against the side plates causing wear from rubbing. Normally, the pump will develop a lubricating film from the material being pumped and lessen the friction = less wear. Gasoline is low viscosity so the effect is not as protective as say, oil. In the past, they enhanced the rotor materials to be more wear resistant but that was expensive. Delphi has a patent on a design improvement that basically provides a balancing port to equalize pressure on the rotors and minimize side plate rubbing. The fuel can then be relied upon to provide lubrication of the rotors.

Dry priming these pumps is known to be bad for them. It’s like anything that is run dry, the wear is increased without lubrication. Running completely out of fuel is really bad for them. Like you mentioned, they continue to run dry until most of the fuel in the lines and rail is exhausted. People who habitually run low or out of fuel is kind of like eating hamburgers every day. You may not notice the effects for awhile but sooner or later it’s going to catch up with you…

I’ve been seeing the news reporta that because of the high gas prices people have been letting theit tanks run low. The logic in doing so escapes me. If the price of gas keeps rising every day, does it not make more sense to keep filling the tank routinely before the price goes up again? I’d rather fill it today at $3.79 a gallon than wait unti tomorrow and have to put in even more gas to fill it at $3.99 a gallon.

There is also the already mentioned risk of fuel pump damage.

There is also the risk of running out of fuel at an inopportune time. Like in a freezing rainstorm at 2:00 AM, or in a bad neighborhood, or on a busy interstate.

I am said to be “out of touch” when I relate that it is hard to believe that a person cannot find a place to shutdown the engine quickly,I ask why is it so hard to comprehend that these gas tanks are run low because the people must wait until payday (or some other source of money) before they can put gas in the car? Very few run the tank down because they think it is a good idea, most run it down because all they have in their pocket is lint. Call it bad money management if you will but that is the answer.

Yet another total load of bilge being espoused by a clueless plastic TV newsreader and unfortunately, providing biased, incorrect, and downright fraudulent information is the norm for media outlets.

The TV station here did one of those worthless car info reports the other day and advice was given that with warmer weather approaching one should be sure to roll down the windows and turn on the heater if your car is overheating. The expert says this should keep your engine cool until you arrive at your destination.
I have no idea how many engines are barbecued every year because of that bogus piece of advice.

There are a great many areas where a safe place is not always readily available. Around many urban areas as well as many too-crowded highways of vintage designs where one can go too far between Jersey barriers before finding a safe spot. Especially at 2:00 in the morning.

I always emphatically told my kids, especially my daughter, that when driving and a light comes on you should ALWAYS try to make it to the first SAFE spot before shutting down. I’ve always told them that the engine can be replaced, but they cannot. Tragically, you may recall that Bill Cosby’s son was murdered when pulled over to change a simple flat tire. I would never never ever want my daughter to pull over until it’s safe. Engines can be valued. My daughter is invaluable.

You make a good point about the reason many are running the tank down.

I really wonder about the sediment theory. In my pothole filled world I have trouble imagining sediment would have a chance to settle to the bottom of the tank, and the fuel filter should handle any sediment.