5 Common Reasons for the Smell of Gas Inside a Car

Updated on May 9, 2018
eddiecarrara profile image

Eddie spent 33 years in the automotive business with Honda. He is an ASE Certified Master Technician and has bruised knuckles to prove it.

Do You Have a Gas Smell Inside Your Car?

"What causes the smell of gas inside a car?" is a question I hear almost every day. A gas leak might make sense as the most likely cause; but more often than not, the cause is unburnt gasses leaking from the engine or exhaust, in places where most people would never even think of looking. Here are five possibilities worth checking out.

1. The Oil Cap's O-Ring or Gasket

A very common place for a fume leak from the engine, which is very easy to overlook, the O-ring or gasket under the oil cap. I find this quite often and it's only a $5 repair. It's a very easy diagnosis, taking about 15 seconds, to determine if this could possibly be the source of your fuel smell. Here’s what to check;

  • Open the hood and look at the area around the oil cap, if you notice oil and debris collecting on the valve cover just below the oil cap, most likely the o-ring is worn out and is leaking, causing fumes from the engine, which "smell like gas” to leak out and be drawn into the HVAC (Heating Ventilation Air Conditioning) fresh air intake located directly below the windshield.
  • Inspect the o-ring for any damage or missing parts. If it looks flat, you may need to just replace it with a new one found at any local auto parts store.
  • Check the oil cap for cracks, if you see any cracks, replace the entire oil cap. It may be a little difficult to get the right one because there are so many different sizes. If your local auto parts store doesn’t have one you could try the dealership or salvage yard.

Sometimes the solution for a problem is an easy fix, but it is often overlooked!

Leaking Oil Cap O-Rings

Fumes leaking from the oil cap o-ring causing a gas smell inside the car.
Fumes leaking from the oil cap o-ring causing a gas smell inside the car. | Source
This oil cap o-ring is flattened and needs to be replaced.
This oil cap o-ring is flattened and needs to be replaced. | Source

2. Loose Spark Plugs Can Cause a Gas Smell

How about them spark plugs? If the spark plugs are not tightened to the proper torque, the crush washer or sealing ring could be leaking fumes from the combustion chamber into the engine compartment right next to—you guessed it—the HVAC fresh air intake, drawing the fumes directly into your vehicles passengers cabin. Here’s what to check;

  • First check to see if all the spark plug wires or coils are in good shape. Remove each one from the spark plugs one at a time, so you don’t mix up the order they are in.
  • If all the spark plug wires and coils look OK, check the torque on the spark plugs. If you don’t have a torque wrench, try this method. Back out the spark plug a little so you can turn the plug by hand. Now tighten the spark plug until it bottoms out by hand. Use a ratchet and socket to tighten the spark plug a quarter turn or until it's snug. A quarter turn would be for example turning the ratchet handle from the 3 o’clock position to 6 o’clock.
  • Check each spark plug one by one until you have tightened each one to the proper torque.

Loose or Broken Spark Plugs Can Allow Gas Fumes to Escape

These are the crush/sealing washers that stop fumes from leaking out of the combustion chamber. If a spark plug is loose, you could get a gas smell inside the car.
These are the crush/sealing washers that stop fumes from leaking out of the combustion chamber. If a spark plug is loose, you could get a gas smell inside the car. | Source

3. Leaking Oil Can Also Cause A Gas Smell

What about oil leaks? Do you have used motor oil leaking out of the engine by an old gasket? Is it weeping down the side of the motor? Maybe it’s dripping onto the hot exhaust system? Used motor oil from inside the engine has unburnt fuel mixed into it, so if it’s leaking out of the motor and onto hot components, it could be the source of your fuel smell. What to check;

  • Open the hood and use a flashlight to look for any dark oily wet spots on the engine.
  • Valve cover gaskets are notorious for leaks. They sit at the top of the engine and absorb the most heat, which causes them to fail sooner then most gaskets. Also they sit right above the exhaust manifold which is the hottest section of the exhaust system. Inspect this area closely for any drips going down the back side of the engine.
  • Look for any smoke coming off the engine when it’s hot. Smoke coming off a hot engine is a good sign there is an underlying oil leak that you cannot see. To find a small leak, you may need to bring the car to your local mechanic. Have them clean the oil off the engine and then add a fluorescent dye to the oil. This dye will glow green when a special UV flashlight is used to inspect the leak area.

Dripping Motor Oil On A Hot Exhaust Manifold

The exhaust manifold is located right under the valve cover gasket. If this gasket fails, oil will drip onto the exhaust and cause a gas smell inside the car.
The exhaust manifold is located right under the valve cover gasket. If this gasket fails, oil will drip onto the exhaust and cause a gas smell inside the car. | Source
Leaking oil on the back side of the motor can smell like a gas leak when the engine gets hot.
Leaking oil on the back side of the motor can smell like a gas leak when the engine gets hot. | Source

4. Exhaust Fumes With Unburnt Gas May Cause Your Smell

Exhaust leaks are another common fuel smell that gets drawn into the passengers compartment via the HVAC fresh air intake, especially if the exhaust leak is close to the engine and before the catalytic converter. An exhaust leak before the catalytic converter can have a pungent fuel smell, because the exhaust includes a lot of unburnt gasses before the converter cleans them out of the system on the way to the tail pipe.

  • Listen for a louder-than-normal exhaust noise, if you accelerate and the engine sounds loud or different, you could have an exhaust leak.
  • Listen for a ticking noise when accelerating. If the exhaust leak is close to the engine, the exhaust leak will make a loud ticking noise like someone tapping on a pie plate, if you hear this type of noise on acceleration, have your mechanic check your exhaust manifold for leaks.
  • If you think you may have an exhaust leak but are not sure, try placing a doubled-up towel over the tailpipe and put your hand over the towel to stop the exhaust from exiting the tailpipe. If you don't feel the pressure building up at the towel, most likely you have a leak somewhere in the exhaust. If you have dual exhaust pipes, you may need an assistant to help block the other tail pipe at the same time.

Ticking Noise From An Exhaust Leak

Leaks In The Exhaust Can Smell Like A Gas Leak

Any leaks in an exhaust system can smell like a gas leak, especially if the leak is before the catalytic converter.
Any leaks in an exhaust system can smell like a gas leak, especially if the leak is before the catalytic converter. | Source

Note: Some mufflers have vents at the bottom to allow moisture to drain; don't confuse this drain with an exhaust leak that needs fixing.

5. Is Your Oil Cap Missing?

How about a missing oil cap? If the oil cap is left off by accident, not only would the smell be unpleasant, but the fumes would be toxic and could literally kill you if the carbon monoxide levels got too high. And the mess a missing cap causes is very difficult to clean up without an engine degreaser. If you just had an oil change or someone just topped off your oil, and you smell gas inside your car, stop and check the oil cap, it could save you from a big mess. What to check:

  • Open the hood and check to see if your oil cap is missing.
  • If the cap is missing, look around for it in the engine area. Most of the time when someone removes the oil cap, they will set it down on top of the valve cover, and if they forget it, it often falls into the engine compartment. If the cap is gone, replace it. Don’t drive the car without it because that will sling oil all over the inside of the engine compartment.

Missing Oil Cap, Check The Engine Compartment

A missing oil cap can cause a huge mess and also cause a gas smell.
A missing oil cap can cause a huge mess and also cause a gas smell. | Source

What Causes a Gas Smell Inside Your Car?

Gas smells don’t have to be complicated repairs; that’s why the problems mentioned here are overlooked so often. When a customer complains of a fuel smell, the first thing their mechanic will look for is a fuel leak. Or they may say, “You must be smelling the exhaust from the car in front of you.” If you smell fuel or gas while driving, check the items listed in this article, if everything looks OK, leave a question in the comment box below and I will get back to you.

Questions & Answers

  • My car is leaking gas and it has troubles starting up, I can smell the gas very strong. do you think it's a failed fuel pump?

    You'll need to find the fuel leak first and fix it. This is probably why your car is starting hard; it's losing fuel pressure.

  • My 1994 Suzuki Sidekick has had trouble starting for years. The only way that I can get it to start is to pump the gas. Recently, when I pump the gas to start it, smoke comes out of the tailpipe and I smell gas in the cab of the car. It has a manual transmission and over 150k miles on it. What is happening?

    I think your engine is getting tired or it may need a good tune-up. If you have not done any basic maintenance like spark plugs, spark plug wires, distributor cap and rotor, engine air filter, etc., I recommend you start with replacing these items and see if the engine starts any easier.

  • Why am I smelling gas when I turn my car on in the morning?

    I recommend checking the oil cap for any signs of leakage, if everything looks ok, have a mechanic check it out asap to be on the safe side, gas leaks can be very dangerous.

  • Why is my car struggling to start when I am trying to turn it on? It has no power.

    If the battery doesn't have enough power to turn the engine over easily, it's possible you just need a new battery. I recommend having someone test your battery and replace it as needed.

  • Suzuki Vitara 99, starts smelling like burnt gas or something like kerosene only when we exceed the 50 mph mark. Could my Suzuki Vitara be leaking or something worse?

    You may be smelling exhaust fumes entering the passengers compartment. I recommend checking the vehicle for any exhaust leaks first or any rust holes in the body where exhaust fumes could enter.

Do you have questions?

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    Post Comment

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      10 hours ago from New Hampshire

      Hi Jana,

      Possible rotted fuel line that just let go? Any signs of leaks under the truck?

    • profile image

      Jana 

      5 days ago

      For two day I smelled gas in my 97 Chevy suburban and then I started it drove then it just shut off what do you think could be wrong.

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      9 days ago from New Hampshire

      Hi Elson,

      Yes the filler cap is on top of the engine where you add oil and it should have an o-ring, sometimes it's hard to see because it's embedded in the cap so look closely.

    • profile image

      Elson 

      9 days ago

      Hi, I'm driving a 2003 seat Ibiza. My car currently smells like gas and it's even worse when I turn on the heating for the windshield. I suspect it's the first symptoms you mention, maybe a missing o cap. I went to buy one and they said it usually comes with the filter. I went to YouTube and found out there are 2 caps, the filler cap and the oil filter cap. I think I mistakenly bought the filler and the o ring together since it clearly is larger than the filler cap. Is the oil filler cap supposed to have a o ring? Because there is no trace of any on mine.. And just to be clear, is the oil filler cap the one on top of the engine where you add oil after checking the oil levels? Thanks!

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      3 weeks ago from New Hampshire

      Hi Jay,

      There are a lot of things that can cause a gas smell as you can see in my article and video. I recommend getting a check over or diagnosis of the smell, if you can smell it all the time, it shouldn't take much to find the source by an experienced mechanic. Let me know if you have more questions, thanks.

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      3 weeks ago from New Hampshire

      Hi Erica,

      It could be a clogged catalytic converter or slipping clutch? Is this a manual or automatic transmission? Is the check engine light on?

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      3 weeks ago from New Hampshire

      Hi Shawn,

      As I wrote in the article it could be exhaust fumes leaking from the engine and entering through the fresh air vent. I recommend having everything in the article inspected like oil leaks, oil cap leaks, spark plug leaks, or any other gaskets near the engine and exhaust.

    • Shawn5162 profile image

      Shawn 

      3 weeks ago from Philadelphia

      Hi, I have a 2016 Dodge Caravan and I drive for Uber & Lyft full time 6 days per week 12 hrs per day. After 8hrs I smell exhaust fumes intermittently and it doesn’t happen everyday! I’ve taken it to the dealership 2 times. The first time they ran an exhaust leak test and couldn’t find anything, but the second time they could smell the exhaust fumes on my clothes and slightly in the cabinet but could not find a leak!! The mechanic also suggested that maybe I was smelling another cars exhaust fumes. But It was happening while I was on the expressway with no other car in front of me! This is really got me worried

    • profile image

      Erica 

      3 weeks ago

      My 2009 Subaru Legacy is struggling to accelerate especially on any incline. When I push on the accelerator to gain speed, the engine revs like it's gaining but it doesn't, and then I smell the fuel. It's been getting poor gas mileage also. There doesn't appear to be any leaks, oil cap is tight and unworn. Could it be the fuel filter, airflow sensor or perhaps a bad or clogged fuel injector? Your thoughts, please.

    • profile image

      Jay 

      3 weeks ago

      Hey Eddie,

      Thanks for the post! I smell gas at all times (when the car is running and when it's idle) in the cabin of my Hyundai Elantra. I don't see any gas leaks like on the ground.. Do you think it would be expensive to get this fixed?

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      4 weeks ago from New Hampshire

      Hi Josef,

      You need to have someone check out the leak to identify what the fluid is first. That could be your whole issue.

    • profile image

      Josef Harang 

      4 weeks ago

      Mercedes sprinter diesel 2500 . I smell gas inside the cabin when is on my lips and mouth is fell like burning the is no leeaking oil or diesel . Also when I start under the van is dropping liquid under driver seats after 2 min its stop can you please help answer why is like this? Thank you Josef

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      8 weeks ago from New Hampshire

      Hi Sabrina,

      Can you see fuel leaking onto the ground? If you can smell fuel leaking when fueling, most likely the filler neck or fuel tank have a leak.

    • profile image

      Sabrina 

      2 months ago

      If my car has a bad gas leak especially when i put gas? You can liyerally smell the gas from my front door?

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      2 months ago from New Hampshire

      Hi Jess,

      Do you smell inside or outside the car?

    • profile image

      jessica 

      2 months ago

      when i turn off my car it smells like gas but there is no gas leak?

    • eddiecarrara profile imageAUTHOR

      Eddie Carrara 

      2 months ago from New Hampshire

      Hi Sherry,

      Did you read the article and watch the video? They will give you several things to check and also explain the common causes.

    • profile image

      Sherry 

      2 months ago

      I have 2007 Nissan Sentra and I am smelling gas what causes this?

    • teaches12345 profile image

      Dianna Mendez 

      8 months ago

      Thanks for the information. This will surely be of use if someone should detect the smell in their car.

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