Gas Level and Fuel Pump/Filter

gasoline
filters
pump

#1

Hello fellow Carl Talk fans… I’m hoping you can help me with a “fact” I’ve heard recently about regularly running my car on a low fuel level and whether its damaging to either the fuel pump or fuel filter? I’m talking about gas levels of 1/4 to 1/8 tank (my garage of cars includes an '04 Volvo XC90, a '98 BMW 740i and a '98 Saab 900 turbo. I’ve never run any of them out of gas and the cars are all well-maintained. I just want to know if I should be concerned/paranoid about frequently letting the gas level drop to the above levels and of the damage that would follow…



Thanks for your time and collective genius!

Me


#2

Letting the fuel level get too low causes the fuel pump to over-heat as it needs the fuel to keep it cool.

I never let my tank go below 1/3 (about half way between 1/4 and 1/2).

Depending where you live, for winter driving refill when the tank gets to 1/2 as you never know when you’ll run into bad weather and traffic tie-ups.


#3

Running the fuel level low is not going to harm the pump. Even when low the pump is full of circulating gasoline just like it would be if it had a full tank.
The exception would be if one got into the habit of running it so low that the car was cutting out and starving for fuel. In this case air from the tank would be inhaled by the pump and the pump would then lose some of the cooling and lubrication provided by the gasoline.


#4

So long as you don’t run dry (or low enough to suck in air), the pump will be fine. As mentioned before, the pump is cooled and lubricated by fuel passing through it. Just don’t make it a habit to run the tank dry, and quit worrying about it. You may have other reasons to keep the tank level up (reducing condensation, reducing the walk to the nearest gas station in a bad neighborhood, having gas to run the engine for warmth when you’re stuck in a blizzard), but don’t go overboard trying to “protect” the fuel pump.


#5

You should NEVER let the tank get below 1/4 full. Doing so can lead to early failure of the fuel pump. And since the pump is inside the fuel tank, replacing it is an expensive proposition, especially on your cars.

In addition, a fuel tank that is more empty than full is more prone to corrosion from water vapor inside the tank. Keeping the fuel tank more often full, rather than more often nearly empty, is best.

Quit being a cheap-skate. FILL IT UP!


#6

I agree with those that say to not worry about it; just avoid running out. If 1/4 tank of fuel was required to protect the pump, it would be an easy matter for the designer to calibrate the fuel gauge to accomplish this so that when the dash indicator read empty, you would still have 1/4 tank remaining.

Keeping 1/4 tank minimum for the pump is an urban legend that is taking forever to die.


#7

I asked my mechanic about this with my own vehicle and he said that it’s fine as long as you fill the tank completely when you buy more gas rather than just put Y dollars worth in. Also keep in mind that even with an “empty” tank, there is still a 1 or 2 gallon reserve of useable fuel in the tank so it’s not like the fuel pump is really going to be burdened. Hope this helps.


#8

You are getting sharply conflicting advice. Apparently there are both Union and Confederate soldiers checking in with their opinions. One side says low fuel levels are harmless, the other side is terrified. It should be perfectly clear that nobody knows the answer for sure.

So Anne, are you any the wiser now?

As for me, I like getting as many miles as possible out of a tank of fuel. I fill it until I see the level of gas in the filler neck and run my cars until they’re sucking fumes. Never caused a problem with either fuel pump nor EVAP system. (I replaced one fuel pump that simply died from old age.) IMHO if you have ever done this once and your car survived, you may safely repeat every time. And if other drivers prefer to take no chances, let them do it their own way.


#9

Well there is some truth to both sides. Running out of gas is not good for any car and unless you really like long walks in the dark on rainy nights in bad neighborhoods, it is not good for you. Running low is not good, but it should not be something you stay awake all night worrying about.

I am trained as an economist, so I would have to say that in the current market, you should keep your tank nearly full most of the time. The price of fuel is going up faster than inflation. Buy now before the price goes up again. :slight_smile:


#10

The Car Guys answered a call from (Calleya?) who asked if contaminants in the bottom of the gas tank would be a problem if the fuel level got low. They agreed that was totally bogus because of the filter, but that there were other (unstated) reasons to avoid low fuel levels. I searched the internet and found as many conflicting opinions as there are here. But, modern tanks are plastic or plastic-lined and they still hold a gallon or so when the gauge says ‘empty.’ This protects the pump from overheating and the tank from rust. With such inconclusive results, I can only assume it’s just a matter of personal opinion. I often let my tank reach empty before re-fueling and have never had a problem. So, I’ll have to continue doing so until some knuckle-head can come up with something that’s not booo-oooo-oooo-gus!
(Maybe it just depends if you are a ‘glass half-empty’ or a 'glass half-full person?)


#11

I don’t think so, at least not on any of the cars the OP has listed.

Just don’t run out of fuel, running low is not a problem.


#12

A low fuel level will not overheat or kill a pump. Even with only a couple of gallons in the tank the pump itself is constantly full of circulating gasoline (pump-engine-return line-back to tank).
If one is in the habit of running it low enough that the engine will hesitate, cut out, or even quit then air is being sucked into the pump and the lack of gas could cause some problems over time.

A far worse problem for fuel pumps is usually the lack of a regular filter change.


#13

Problems with frequently running tank low: Killing the pump if you run out. More condensation = more water in fuel. Evap tests won’t run below certain level, and empty tank puts a bigger load on Evap system.


#14

When a pump gets weak, it may fail to pump properly with a low fuel level since it is harder to pump.
.
I guess to some extend keeping it low will make it work harder, but I doubt if it greatly reduces pump life.
.
Running very low is a different matter, then you get overheating and other issues.
.
The real question is my book, is why would anyone do it? I had a friend who would always be running very low or totally dry. Her excuse was she did not have the money to keep it full??? Come one now, it cost the same to keep it full as it cost to keep it almost empty. Since there is at least a possibility of damage for allowing it to go low, it would save money by keeping it fuller.


#15

No cost advantage, just time. I sometimes drive 1000 miles in one day (about 3 fuel stops) and fill-up after it gets below 1/4 tank. If I filled up sooner, I would probably have to make an extra stop.


#16

It seems to me that the less air that goes into the pump, the better off it will be. Avoid all possibility of damage by filling up when the gauge gets near a quarter. Why worry at all?


#17

I agree with the “so long as you don’t run it out” camp. I will mention that, because running a modern fuel-injected pump-in-the-tank car out of gas is so bad for it, there’s usually two to three gallons between E and where you actually run out of gas, so when you’re on 1/4, you’ve probably got a good 5 or 6 gallons left in there, which can be hundreds of miles on some cars these days! On older cars, E meant empty and if you were on 1/4 tank you were pushing it.