For every car I’ve ever owned, I’ve always waited until the low fuel light came on or until I was at < 1/8th of a tank of gas to refill. I’ve never had any problems doing so. The only time I ever make a conscious effort to keep a full tank is in winter.
I was recently told that this puts excessive strain on the fuel pump and can cause premature wear out. Is this the case? If so, what is the lowest amount of gas we should keep in the tank to avoid straining the fuel pump?
The fuel pump is submerged in the gas tank, and the gasoline serves as coolant for the pump. Low gasoline level can lead to overheating of the pump.
I don’t like to let my car’s gas tanks get below 1/4.
Keeping the tank closer to full also helps minimize condensation of water in the tank.
The fuel in your tank helps to cool the electric fuel pump, which frequently generates a fair amount of heat as it runs. Thus, chronically running the car with a very low level of fuel in the tank does expose the pump to more heat than if it was run with a higher level of gas in the tank. Heat does take its toll on most things, including electric motors.
All of this leads me to the inevitable question:
Why not just fill the tank sooner, rather than always waiting until the last possible moment? If you made it a practice to fill the tank every time that it fell to the 1/4 mark, you would not spend any more time in gas stations than if you consciously decide to wait until it is almost empty.
Thanks for the info.
I drive about 280 miles a week and have a gas tank that can get me about 300 miles. It’s a lot easier to only have to fuel up once a week vs. twice. I was also completely unaware that I was causing damage to my car; I re-read my owner’s manual and it made no mention of the fuel pump. I’ve also never had to get one replaced after several decades of driving.
Is 1/4 tank considered the lowest level one can let the tank run down to?
Others will disagree with this, and it depends on the car that you have. Mine, like many, has a small bucket around the pump that keeps it cooled by gasoline, even if the tank is very very low. The pump will only be damaged if you actually run out of gas. As long as there is a gallon still in the tank when you fill up, you will be okay.
If you wait for the light then usually most cars have 2gallons+ left.
My wife has done this on all her cars run 150k-200k in her ownership and no fuel related problems.
I see your point in running from full to close to empty rather than make frequent fuel stops. What kills the fuel pumps prematurely are drivers that run near empty and then fill with a $5 or 10 and therefore are constantly running without much fuel in the tank.
The fuel pump and tank designs differ and some cars are more prone to heat related fuel pump failures than other makes and models. As long as you fill your tank you aren’t running on low fuel too much and your fuel pumps have not been problems for you. Yet, refilling the car at 1/4 tank most of the time reduces your risk even further.
People like to have explainations for events and the “low fuel level” damages pumps satisfies this desire for an explaniation. The story keeps getting repeated from person to person and it becomes much easier to get on the band wagon than say"is any evidience of any type other than anecdocial available?"
You will get "low fuel level causes check engine lights " also.
I would be spending all my time on the side of the road (or with a check engine light on) if the claim was true.
There is lots of “urban legend” stuff surrounding this subject… In most tank / pump designs, the actual pump is mounted high in the tank and is only submerged when the tank is full or nearly so. Since the fuel system constantly is returning excess fuel to the tank in a closed loop constant pressure system, the fuel flowing through the pump keeps it cool, if indeed it needs to be kept cool…This whole argument depends on the fallacy that in-tank fuel pumps are somehow subject to overheating when in fact I don’t believe that’s the case…
Overheating fuel pumps inside a closed gasoline tank are NOT a design feature that is built into these pumps. They don’t fail because they overheated. They fail because they wore out or the flex-lines that connect them inside the tank rupture and pressure is lost. Once fuel pressure is lost, the engine and fuel pump are shut down long before the pump “burns up”…
Just a slight correction here. Most fuel systems (being made now) are now return-less systems, so there is no constant circulation.
I do agree that fuel pumps don’t overheat or fail due to low fuel levels. I do know that they can fail due to no fuel conditions. I have seen older pumps that couldn’t handle the stress when run dry. I have also seen the fuel pump fuse blown when someone ran out of gas. Of course, there are many more examples where running dry did not cause any failure.
The pump will only be harmed to some degree if the fuel level drops low enough to cause symptoms such as bucking and jerking and it make take a number of episodes like this to actually kill a pump. A one time deal won’t do it.
As long as there is enough gas in the tank to keep the pump filled (no bucking of course) then simply running the level down low will hurt nothing.
The fiberglass filter “sock” that lays in the bottom of the tank and serves as the fuel pick-up for the pump will allow almost every last drop of fuel to be drawn from the tank…At that point, fuel pressure is lost, the engine dies, and the pump shuts down within a few seconds.
So back to the OP’s question…When you have 1/8 tank of fuel or even less, you are NOT damaging your fuel pump. These pumps, like everything else in the vehicle, have a “mean-time-before-failure” designed into them, the point at which 50% have failed and 50% still operate… That failure point is built in…Nothing lasts forever.
I had to replace my fuel pump at 125K miles and am sure I drove many miles near empty. The pump never did quit but it looked like it was supposed to move up or down with the gas and it was hanging up. Even the gage was showing empty when in fact it had plenty of gas. So I doubt that driving with low gas harms a fuel pump (much).
That is an anti-slosh baffle designed to keep the pump from starving when the vehicle attitude/speed changes abruptly. The level is no higher than the rest of the tank when the fuel is not sloshing around. It has slots in it to allow fuel into the baffle area but small enough to prevent it from sloshing away too quickly.
There are people who will insist that running your tank down until the fuel light comes on is harmful. I say, nonsense! If that is true then it’s a damned poor design. Early fuel pump failures are more correlated with manufacturer than fueling habits.
Purely anecdotal, but consistent over several different makes and models I’ve owned, in my experience I almost always run a tank down until the fuel light comes on or the needle is just hitting the empty mark before filling up. I have never had a fuel pump failure, and I routinely keep cars well over 100,000 miles.
Of course, it does no harm to fuel up sooner, but the manufacturers put those fuel warning lights in there knowing the parameters of how much fuel is left in the tank and how the fuel pump works. They’d be foolish to intentionally set owners up for fuel pump failures. That kind of bad reputation is hard to overcome.
This topic comes up here on a fairly regular basis but with long periods in between. The last time I posted a rather lengthy and comprehensive argument citing a particular FAA aviation investigation that concluded the cause of a crash was fuel pump failure resulting from damage caused by chronically running the pumps low on fuel. The pumps used in that plane were a similar design to automotive pumps. As you might expect they are designed and built more robustly than automotive pumps for obvious reasons. The FAA is pretty well known for comprehensive analysis following a crash and I believe their results are beyond dispute by the average person with enough mechanical and electrical knowledge to be dangerous. The point being, if those pumps can fail due to chronic low fuel conditions, what would make you think the el-cheapo pumps used in automotive applications would be immune to the effects? Anyway, my 3c.
GM made a error, they meant to to have the low fuel warning light say damage your pump light, how could a company as big as GM make that error.
I suspect one of the design criteria for automotive pumps is that they must be able to run dry without damage for a given length of time…The aircraft story sounds like more urban legend stuff…Pilots DO NOT EVER routinely run on low fuel…In aviation, that’s a big, big, no-no…Fuel pump failure in aircraft that cause engine failure is so rare it’s statistically unimportant. In aircraft, the PILOT can control fuel transfer pumps and perhaps run them dry…Not possible in automotive usage as the driver has no control over the pump.
What about the condensation idea–which is true for home heating oil tanks-- or that there is more sediment at the bottom of the tank (is there?)which will be a bit rough on filters or engine?
Pump damage due to a low fuel level is just an old wives tale and is just one of a thousand other automotive old wives tales.
If the engine is running fine this means the pump is full of fuel which means the pump is being both cooled and lubricated by the gas that is constantly being recirculated through it.
The pump does not even have to be submerged in gasoline to be both cooled and lubricated. If that were the case then then many fuel injected cars (VW, Volvo, Merkur, etc, etc.) wouldn’thave made it more than 10 miles from new because their pumps were externally mounted.
Consider the number of custom build cars with F.I. systems in which pumps are mounted externally to the tank.