Why do today what can be put off until tomorrow? The procrastinator’s dictum sounds dumb when you put it down in digital ink, but when it comes to filling our gas tanks, many of us only do so when it’s absolutely necessary. Turns out, getting stranded on the roadside isn’t the only risk when you’re running on fumes. Below are five reasons why topping off your tank should be added to your list of car maintenance priorities.
Gasoline not only fuels the vehicle, but it also functions as a coolant for the electric fuel pump motor. In modern cars, this pump sits in the middle of the gas tank filled with cool gasoline. A near-empty tank can cause the fuel pump to suck in air and overheat, causing increased wear to the pump.
Each time you neglect pumping gas, gunk from the bottom of the fuel tank could get caught in various components of the vehicle. This sediment in your tank can foul the fuel filter. If the fuel filter doesn’t catch the sediment, you run the risk of clogging a fuel injector. This is less of an issue today with modern heavy-duty plastic fuel tanks, but in older vehicles with metal fuel tanks, rust particulate can be a serious danger.
When a diesel runs dry, the injector pump fills with air and the vehicle won’t start by simply adding more diesel fuel. A tow truck and mechanic may need to get involved to tow the vehicle, remove filters, pressure-blow the fuel lines before adding fuel and priming the engine. Because of this, maintaining a full tank with a diesel engine is even more critical than with a gasoline engine.
The most common concern with allowing your fuel to run low arrives once the mercury dips below freezing. That’s because the condensation that builds up in your fuel tank when it’s low has a greater chance to get sucked into the fuel lines and freeze. Not only can this mean your vehicle won’t start (with frozen water blocking the flow of fuel to the engine) but the lines themselves may become damaged by the expansion and contraction of the freezing water.
Some will argue that because the gas tank is lighter when its low, a low tank will give the car more fuel efficiency. A lighter load does require less gasoline, but the weight of a full fuel tank is not significant. A gallon of gasoline weighs only 6.3 lbs. (for reference milk weighs 8.6 lbs. per gallon), so even in most large vehicles the total weight of a full tank is under 250 lbs. Your car may actually be less efficient when the tank is near-empty, as more air in the tank can increase fuel evaporation.
Running out of fuel completely is the biggest danger of allowing your tank to run low, especially during the temperature extremes of winter and summer. Additionally, when an engine dies brakes and power steering can be lost, so running out of fuel at highway speeds can be hazardous in itself. Besides, delaying the expense of a fill-up doesn’t reduce long term expenses, so it is never worth becoming stranded and putting yourself or your family in danger.
Along with keeping the fuel tank full, make sure to have a weather-appropriate vehicle emergency kit in your vehicle. Not all of us are as lucky as Kramer on Seinfeld.
Some of you might only be allowing your fuel to go flirt with E because you struggle finding time to fill up. But weigh the inconvenience of a five-minute fill-up when you have time after work or on the weekend versus when you have an appointment to get to or a job you’re already late for. Making frequent fill-ups a higher priority avoids last minute emergencies. And all this doesn’t even cover how late you’ll be if you actually run out of fuel.
Skimping on fueling up doesn’t save money and could actually lead to expensive repairs and/or a costly tow job. Habitually running the car to empty could lead to fuel pump damage and a repair potentially costing hundreds or even thousands in parts and labor. Filling up can be painful when prices are high, but it is an investment that will protect your vehicle and save you more time and money down the road.
Trying to save money while driving? The tires are a great place to start. How to save money by maintaining your tires.
How far can you run a 2000 volkswagon beetle low on fuel?
It’s interesting how cars may actually be less efficient when low on fuel due to the potential for evaporation. I just purchased a diesel lawn mower last month, so I need to order some fuel for it before the weather warms up. I will be sure to keep it topped off throughout the summer to maximize efficiency. http://www.fuelmanhawaii.net/services
It is said that if it is full tank that the fuel consumption is very efficient or fuel consumed somewhat slowly. Is this true or a myth?
Great post, thanks for sharing. Picked up some good and valuable insight
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Is it ok to fill up my gas tank as soon as the handle pops?
A couple quick counterpoints:
1) on fuel evaporation … since the late-1970s/early-1980s, vehicles have been equipped with non-vented fuel systems that include an evaporative emissions control system (usually abbreviated as simply “EVAP”) designed to keep fuel from evaporating to the outside air. Any fuel that does evaporate would be ingested into the engine via the EVAP system courtesy of the engine’s own vacuum, so fuel that evaporated within the tank wouldn’t be lost or wasted — it gets burned, just like normal. So the evaporation problem is a myth.
2) cooling effect on in-take fuel pumps … while it’s true that the fuel pump would be kept marginally cooler while submerged in fuel, many/most in-tank fuel pumps are mounted high up on the sending unit, to allow room for fuel straining sock/filter and the float assembly. As a result, once the fuel level reaches 3/4 or 1/2 tank, the fuel pump is generally exposed anyway. But that’s ok, because electric fuel pumps tend to receive ample cooling from the fuel flowing through them. Keeping them submerged isn’t strictly necessary. They’re located in the tank because most electric pumps work better as “pusher” pumps, rather than as “puller” pumps.
3) low fuel level causing evaporation … sure, as the fuel level decreases, the remaining volume is filled with air, which could allow for evaporation, but as I pointed out in point 1, evaporation isn’t a problem in modern cars, because the systems are closed systems. Any fuel that evaporates will either be burned by the engine anyway, or when eventually fall out of suspension in the air within the system as liquid fuel again as the temperature cools down. Besides, a bigger concern than low fuel level would be how the fuel gets aerated as it returns to the tank via the return line. As the returning fuel reaches the fuel tank, it’s either allowed to squirt back onto the fuel in the tank, which would have a similar effect to running your kitchen faucet into a pan — it creates lots of bubbles — or it could be introduced lowed in the tank, perhaps beneath the surface of the fuel, but it still contains plenty of air/bubbles because the return side of the fuel system isn’t fully pressurized. Regardless, aerated fuel isn’t really a problem nor is any evaporation caused by it, because (again) the system is closed and doesn’t allow the fuel to escape, except through the EVAP system or via the pressurized fuel line to the engine, and in either case, the fuel just gets burned like usual.
4) Weight … 250 additional pounds shouldn’t be considered significant? That’s more than the weight of an average adult … even overweight Americans. And since most cars and light-duty (1/2-ton) pickups and vans only have about a 1000 pound “cargo” capacity (including passengers and the driver), that’s the equivalent of 1/4 of the car’s cargo capacity. Sounds pretty “significant” to me. That extra 250 pounds will require the engine to make more power to get it moving, and that means it’ll have to burn more fuel. Will the difference be dramatic? Probably not. But to call 250 pounds “not significant” is disingenuous.
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I agree with other others: Great post, I picked up some good and valuable insight. I also like some other peoples’ replies that go into more detail. I am 70+ and grew up with 1960’s cars (I have 56 Tbird) and I (unfortunately) think I know ‘enuf’ to get by from high school days.
Sidebar: Unrelated to this article, I painfully discovered why my self-installed Pertronix ignition acted so haphazard on my rebuilt Tbird, 312 motor (and downright ‘destructive backfiring plus run-on’) to my newly resprayed engine bay and rebuilt engine: poor grounding of regulator. The mechanic overlooked cleaning/chasing the regulator mounting holes for paint removal to insure good grounding. Indeed, there is even a small ground strap for the regulator, but as described that hole and strap surface were never properly prepared.