The Complete Guide To Dealing With Bad Gasoline In Your Car

by | Apr 10, 2020

We take gasoline for granted.

For most of us, it’s as simple as putting gas in, and then driving away. These days, it’s very rare that you’ll get bad gas from a gas station. In over 18 years as an auto mechanic, I’ve never seen someone’s engine damaged by bad gas.

It just doesn’t happen as much as it used to.

But it does still happen.

Back in 2012, over 4.7 million gallons of gas were recalled from BP stations in Chicago, Northwest Indiana, and Milwaukee. The bad gas, in this case, was contaminated with polymer residue, which doesn’t burn in automotive engines and can cause damage to the engine.

Generally speaking, bad gas is usually the result of contamination from your fuel tank or fuel line. It can be the result of your car sitting for an extended period of time, or from water making its way into the fuel tank.

By the time you’re finished reading this guide, you’ll be an expert in diagnosing if your car actually has bad gas, as well as correcting the problem if it becomes an issue.

You’ll learn everything you need to know – and probably some things you don’t need to know.

What Causes Gas To Go Bad?

Gasoline doesn’t stay good forever. The countdown starts as soon as you expose gasoline to air. After around 30 days or so of sitting in your fuel system, your gasoline starts to oxidize.

When gasoline oxidizes it can gunk up your fuel system by turning into varnish which can coat your fuel system and engine. As gasoline degrades, it goes from clear in color to looking more like apple cider. This “apple cider” gasoline then begins to gum up your fuel system and your engine.

Even worse, today’s gasoline often contains ethanol. When these deposits form, the ethanol in them attracts water from the atmosphere (it’s hydrophilic for all you chemistry nerds).

Generally speaking, old gas in your car isn’t the end of the world if you’ve let it sit for only a couple of months, but if your car has been sitting for 6 months or more, you can run into some problems and you may need to use something like Seafoam.

We’ll get into what exactly you need to do in a bit.

Age is the most common cause of bad gas, but it’s far from the only one.

Water can also get into your gas tank. This can be caused by a loose gas cap, or from condensation. It’s also possible that water can make it in from the pump itself – although this is getting more and more uncommon.

Besides age and water, you may also have contaminated gas from a cracked fuel line, or from flakes coming from your gas tank.

What Are The Symptoms Of Bad Gas In Your Car?

Bad gas is fuel that doesn’t combust as expected. With that in mind, most of the symptoms are related to the car not running as expected.

Your car relies upon fuel being delivered to the combustion chamber and igniting optimally. When this doesn’t happen, the car often hesitates and suffers from a lack of performance. With that in mind, some symptoms of bad gas to look out for include:

1: Difficulty Starting Your Car

If your car cranks but won’t start, it could mean that you have bad gas. Contaminated gas doesn’t provide enough power to start the engine. However – if your engine doesn’t start, you shouldn’t automatically assume you have bad gas. Anything from bad spark plugs to a busted fuel pump can cause your engine not to start.

If you have a lot of bad gas in your tank, this can cause your car not to start in some cases.

2: Sputtering Or Pinging Sounds When The Car Is Idling/Driving

Bad gas doesn’t combust evenly – which can cause your engine to sputter or ping. Listen to your car both at idle and while driving at moderate speeds. These noises aren’t the smoking gun on their own, because they can also be caused by a bad fuel filter.

3: Stalling While Driving

If your gas is contaminated with sediment or with water, it’s possible that your car may stall while you’re driving because the fuel is not combusting correctly. This only happens in extreme cases, so more likely than not, it’s not something you’ll have to worry about.

4: The “Check Engine” Light Coming On While Driving

Bad fuel can cause your car to run lean. If you have an OBD-II code reader, the code will almost always relate to your engine running lean.

5: Burning More Gas Than Usual

When you have bad gas, your engine will have to work harder than normal to produce the same amount of power. This can show up as your car burning more fuel than usual. On its own, this isn’t a smoking gun, but if you notice it together with the other symptoms, pay attention.

6: Trouble Accelerating

If you have bad gas, it’s common for you to have trouble accelerating or going up hills or other steep inclines because bad gas doesn’t burn correctly.

7: Speed Changes While Driving Without Pressing The Gas Pedal

Bad gas can also cause your car to abruptly change speeds while driving. You may notice a sudden slow down, followed by a surge of speed.

What Are The Symptoms of Water In Your Gas Tank?

The symptoms of water in your gas tank depend on how much water gets into your gas tank. If there’s only a little bit of water, you might not notice it at all.

But if there’s a lot of water in the tank – you’ll definitely know.

The main thing to watch out for is hesitation when you try to accelerate. When there’s water in your gas, your engine won’t be able to perform up to standard. The more water in your gas, the worse this will get.

The other symptoms I’ve already covered above.

So, Can Bad Gas Damage Your Car?

The answer is yes – but for it to get to that point you need to really let things go for a long time. Bad gas can form deposits that can cause issues in your engine. Again, this is very rare and probably won’t happen, but it’s good to know.

However, if you get bad gas from a gas station, you could be in for quite the repair bill. Although I’ve never seen the damage personally, I have seen reports ranging from $1,000 to $2,500+.

How To Get Reimbursed For Bad Gas

As I previously mentioned, most bad gas is probably not the kind you’ll be able to be reimbursed for. For example, if your gas goes bad because it’s old you’re not going to get reimbursement.

However, if you put gas in your car and it almost immediately starts coughing and sputtering, then you may be on to something.

To prevent yourself from getting the shaft, you need to make sure you get a receipt. If you can prove you got bad gas from a gas station, then you’ll be able to get reimbursement.

More likely than not, you’ll be paid through the gas station’s insurance policy. You may also want to call your state’s consumer protection agency to report that you got bad gas to prevent others from getting burned as you did.

With that being said – how can you be sure if you have bad gasoline or not? You test for it.

How to Test For Bad Gasoline

The first thing you should do is ask yourself if it’s possible that your gasoline was contaminated due to your own error. Whether that was through letting your car sit, or through a loose gas cap, or something similar.

If you can rule these out, then it’s somewhat difficult to test the gasoline without special tools.

 A fuel test procedure and kit (without sending out to a lab) involves 3 steps.

  1. The first involves lowering a probe to the bottom of the tank with a paste that changes color if it touches moisture. The probe almost resembles a bicycle cable in a clear sheathe. This requires the probe and the color-changing paste.
  2. The second involves retrieving a sample of the gasoline. Place the gasoline in a graduated cylinder. Add some amount of windshield washer fluid. Cork the sample and shake the tube. Wait until it settles. Compare how much gasoline you put into how much is left after everything settles. This shows how much alcohol is in the fuel. It should be no more than 10%. All this test needs is a graduated cylinder that can survive gasoline. This is the easiest thing to acquire.
  3. The third involves retrieving a sample of the gasoline. This test measures the volatility of the gas known as Ried Vapor Pressure and requires another special testing tool. Chill the gasoline and tool on ice for 30 min. Pour the fuel into the tool and close it. Place the tool into hot water for 10 min and measure the water temperature. Read the pressure from the gauge on the tool. Compare the pressure and temperature to a table that comes with the tool.

How To Get Water Out Of Gas

If you have water in your gas, the first step is to figure out how much water you have in your tank. If your car is still drivable, chances are you don’t have too much water in your gas tank.

However, if you’re having serious performance issues – then you’ll need to go another route.

In this case, you have a few options.

They include using a product like Heet or by doing it yourself with dry isopropanol alcohol.

Considering Heet is about $3 on Amazon, it’s usually the easiest option.

If Heet or isopropanol alcohol doesn’t fix the problem – then you’ll need to siphon the gas out of your tank.

Get a fuel siphon, and then feed the tube into your gas tank and get pumping. Pump the siphoned fuel into a clear container so you can inspect it, and then refill your gas tank with good dry fuel.

How To Fix Bad Gas

Fixing bad gas, on the other hand, is much simpler. If you have true bad gas – not old gas, or waterlogged gas, then you’ll need to siphon the gas out of your tank and pump new gas in.

Don’t mess around with this, because bad gas can cause damage when it does happen, even if it only happens rarely.

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