Muffler Delete & Gas Mileage (Everything You Need To Know)

By September 14, 2020Performance Modification

There are many myths and conceptions when it comes to muffler delete. In this article, I want to discuss the relationship between muffler delete and gas mileage.

In short, the answer is no. Muffler delete will not impact gas mileage in any way. Muffler is a sound suppressing device that reduces the intensity of sound waves from combustion. If you just performed a muffler delete and noticed a change in gas mileage – then likely it’s caused by something else like malfunctioning O2 sensor or simply a placebo.

If you are just researching before actually doing it, then don’t worry – muffler delete will not impact your gas mileage. But should you do a muffler delete though? Let’s go in detail about muffler delete and what you need to know before doing it.

Recap: What’s Muffler Delete?

For the beginner enthusiasts, muffler delete means removing the muffler from your car. A muffler reduces the noise of your car significantly – this means if you remove the muffler, you can make your car sound way louder. 

The aggressive sounds of cars are cool as hell – right? Why would car manufacturers reduce the car sound in the first place? That’s because the majority of people who are not car enthusiasts like us – prefer quiet, reliable and fuel-efficient cars.

Also, car manufacturers must follow regulations set by the government. This means making sure their car noise goes below a certain level (dB). For example, California states that a car may only produce sound up to 95 dBA or less. 95 dBA is actually quite loud – it’s as loud as a food processor.

Image of straight pipe exhaust
Exhaust pipe with deleted muffler

Recap: How’s Fuel Used In a Car?

We all know fuel is needed for a car to function – but how exactly do cars use fuel? We need to understand this to see how a muffler delete can impact mileage. 

You see – a car generates combustion to produce power and move its wheels. A combustion is a controlled explosion that’s generated by igniting fuel in the combustion chamber. Also note that combustion needs Oxygen to exist. This basically means a combustion requires both oxygen and fuel in the combustion chamber. 

On the other hand, combustion also creates toxic exhaust gases as byproducts. At every interval, exhaust gases leave the combustion chamber into the exhaust pipe where they eventually exit the car.

It’s important for exhaust gases to leave quickly.  Otherwise, there won’t be enough room for new oxygen to enter for the next combustion – resulting in weak combustion and thus, reduced horsepower.

Will Muffler Delete Improve/Reduce Gas Mileage?

As I said above, muffler delete will not impact gas mileage in any way. However, I know that there are many conflicting myths out there regarding muffler delete. Some say muffler delete improves gas mileage while some say it reduces gas mileage. Let’s look at what they say.

Myth #1: Muffler Delete Improves Gas Mileage

In case you didn’t already know – heavier cars use more fuel to move. This is logical – the heavier the load, the more power is required. What I think is not logical is removing a muffler reduces so much weight to the point gas mileage is improved.  

I mean… What do you think? An average car weighs 2,800 pounds. Whereas a muffler weighs 15 pounds? 30 pounds? I don’t know exactly but you get my point – the weight from removing a muffler will not improve gas mileage.

Myth #2: Muffler Delete Reduces Gas Mileage

Earlier, I mentioned that exhaust gases need to leave the combustion chamber for new oxygen to enter for the next combustion. If you make exhaust gases leave quicker, more room is available for oxygen to enter – which can result in a bigger combustion and more horsepower if more fuel is ignited. 

The theory for this myth is that removing the muffler from your exhaust system will reduce the pressure in the exhaust pipe (backpressure) – allowing the exhaust gases to leave much more quickly from the car. Thus, more oxygen entering and more fuel can be burned to boost horsepower.

This works well in theory but not in reality. The reasons?

  • You need to tune your car to inject more fuel to make use of the supposedly reduced backpressure and extra oxygen. Will you tune your car after muffler delete? I don’t think so.
  • Muffler delete will not reduce so much backpressure that it provides such impact.

To conclude, don’t worry about muffler delete reducing gas mileage. 

Common Causes Of Poor Gas Mileage

If you do experience reduced gas mileage after muffler delete, then I suspect something else is causing that and you should get it checked out. Here are the common causes of poor gas mileage.

1. Malfunctioned Oxygen Sensor

Oxygen sensor dictates how much fuel to inject for the next combustion. It does so by reading the amount of oxygen leftover in the exhaust gases. Too much oxygen leftover means not enough fuel was injected. Therefore not all of the oxygen was utilized and performance of the car became subpar.

To fix this, your oxygen sensor will tell your car’s computer to inject more fuel for the next combustion. This is good if the reading is correct. Otherwise, extra fuel will be injected unnecessarily. 

Is it possible that you caused your oxygen sensor to malfunction while trying to remove the muffler? 

Oxygen sensor mounted on exhaust
Oxygen sensor mounted on exhaust pipe

2. Air/Fuel Ratio Tuning

Did you bring your car for a tuning after performing the muffler delete? It’s common to lower the air/fuel ratio in a car so that it injects extra fuel for each combustion. This wastes fuel but it means your car performance is always at its peak. 

Your tuner might have misunderstood and tuned your car with a lower air/fuel ratio to boost horsepower – which makes your car more aggressive but also not fuel efficient!

3. Too Much Stuff On The Trunk

Earlier I mentioned that weight plays a factor in fuel consumption. Heavier load will need more power to move – which means more fuel is ignited to deliver that power. 

By any chance, have you been leaving heavy stuff on your car? Common stuff like golf clubs, extra passengers, extra tires, etc – you get the point. This seems like a trivial thing but it’s the easiest thing to do when it comes to saving fuel.

Remove items on car to save fuel
Remove unnecesary load from car to save fuel

4. Changed Driving Habits

I think this is the number one cause for experiencing poor gas mileage after muffler delete. You like the new sound of your engine so much that you subconsciously rev up your engine any chance you get.

This makes you drive more aggressively than before. Sure it’s fun, but you will use much more gas from doing so. 🙂

Things To Know Before Doing Muffler Delete

Now that you know muffler delete will not impact your gas mileage, don’t immediately go and remove your muffler just yet! Here is a list of things you need to know when considering a muffler delete. Some are good, some are bad and some are horrible!

1. Muffler Delete Will NOT Void Warranty

If you are in the United States, you are protected by the Magnuson-Moss Warranty Act – which states that in order to void warranty, your dealer must prove the problem is caused by your modification or aftermarket installationI cover more about muffler delete and its warranty in this article

2. Muffler Delete Is Inexpensive

The idea of muffler delete is removing the existing muffler and replacing it with extra exhaust piping. The cost you need to bear includes cutting off the muffler and welding the exhaust piping in place. 

If you have the right tooling, you can do it yourself for free. Otherwise it costs probably $50 with the labor and extra piping. Here’s a YouTube video showing you how to perform a muffler delete.

3. Muffler Delete Will Not Improve Performance

Muffler is simply a sound suppressing device. Removing it will not gain you any improvement in performance. A lot of people argue that removing the muffler can reduce backpressure which results in extra horsepower. 

It works in theory but in reality removing a muffler will not make any noticeable difference to your horsepower. You perform muffler delete for the sound improvement, not horsepower. For horsepower look into things like turbo – you will gain serious horsepower with it. 

4. Sound Could Be Deafening

Sound changes from a muffler delete is a double edge sword. Yes – the engine sound will be much louder and more aggressive. But it could be too loud to the point it’s deafening. Oftentimes, muffler delete is cool and sexy for the first week. After that it will be a nuisance for you and your surroundings.

This is why reversing a muffler delete is very common. I even wrote about it right here. I won’t invest my time writing about a topic if no one is interested. 🙂

5. Muffler Delete Could Be Illegal 

In strict states like California, muffler delete could be downright illegal. Technically speaking the law states that your vehicle needs a  working sound-suppressing device at all times. If every car comes with a muffler and resonator, won’t muffler delete be legal? I would say that’s a gray area…

Even if the above is true, the law also states that an engine sound can only go up to 95 dBA – which is quite loud in my opinion. But muffler delete could get much louder than that – especially during a cold start.

If you are not a fan of getting into conversation with traffic officers, then stay away from muffler delete.

6. Poorly Done Muffler Delete Can Cause Rusting

That’s right! If you do not cut and mend the exhaust pipe properly, your exhaust system is at risk from rusting. Rusting exhaust pipes is very common – especially if you are driving under damp roads with lots of still water.

Once there’s rusting on any part of your exhaust pipe, it could grow as time passes and eventually snap your exhaust pipe in two. Research carefully on how to perform muffler deletes before you decide to do it. Even better if you can get a pro to do it.

Should I Perform Muffler Delete?

With all that being said, I don’t recommend you do a muffler delete. If all you look for is an improved sound, then there are many other better ways in achieving so.


The best way is to upgrade into an aftermarket muffler from a reputable brand. If you are looking for one, I suggest you look into Flowmaster Super 40. They produce a great aggressive sound while not being so loud. I cover why I choose the Super 40 in this article

The Super 40 costs about $80. Maybe $100 with install. If that’s too expensive for you, I have an article where I talk about the affordable way to improve sound.

Flowmaster super 40
Flowmaster super 40 Muffler
Ifandi L.

Ifandi L.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.

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