Exhaust Steel Grades Compared: 304 vs 409 Grade Stainless Steel

So you’re looking at upgrading your exhaust, and you’re thinking ‘I’ll just get the cheapest- as long as its stainless steel the results should be the same, right?” Definitely not.

An exhaust made from 304 grade stainless steel can withstand harsh terrain, and maintain its toughness in both hot and freezing temperatures. An added bonus is 304 grade steel looks great and is easy to maintain- an investment that will last for years to come. And after all, you spend thousands of hard-earned dollars on buying your vehicle- why would you compromise on its performance by installing a second-rate system? Here we cover off on why 304 grade stainless steel is superior to 409 grade, but first…


The material of an exhaust directly affects the strength and lifespan of the system, as well as the sound of its note. Aluminised or mild steel is lightweight and affordable, which is why it is commonly used in stock exhausts. This comparison shot by customer @baoscruiser shows just how damaged a low quality stock system can get.

Lining up a stainless steel exhaust next to a stock exhaust gives you a pretty good idea how vehicle manufacturers keep the costs down- the quality and performance of a stock exhaust is deliberately restricted to meet the broadest range of demands in the most cost effective manner. On the other hand, a quality stainless steel exhaust will likely outlast the life of your vehicle.

The properties of stainless steel make it a considerably superior material in terms of quality, performance and longevity.  The high temperature resistance of stainless steel also makes it an excellent choice of material for aftermarket exhausts. Another comparison shot by Torqit dealer Baw Automotive shows the extent of rusting commonly found on a stock system.

When it comes to stainless steel, the two most common grades used in the automotive industry are 304 and 409 grade. The key difference between the two grades is the percentage of chromium and nickel found in each metal, which changes its strength, hardness and resistance to corrosion. Although both grades can look identical at a glance, there are substantial differences to be aware of when it comes to getting value for money.



  • 304 Grade is an austentitic stainless steel, meaning it contains high amounts of chromium and nickel. These properties give it the perfect mix of strength and resistance to corrosion.
  • The high nickel content protects against fatigue and rust, plus provides excellent weldability and toughness
  • The chromium also prevents rust, and guards against wear and high temperatures while increasing the tensile strength of the steel
  • As 304 grade is a premium quality steel, an exhaust made from this material is more expensive than 409 grade.
  • It is suited to a variety of harsh climates and conditions
  • 304 grade is visually appealing
  • It is unlikely to develop rust, and can be polished back to the original finish if it develops a golden-brown appearance.


  • 409 Grade is a ferritic stainless steel, meaning it contains smaller amounts of chromium and nickel. As a result, 409 grade is weaker and more likely to rust.
  • It has a shorter lifespan than 304 grade steel as it is less tough and corrosion-resistant
  • An exhaust made from 409 grade is cheaper due to the lower quality of the steel
  • As it contains up to 90% iron, 409 grade quickly shows surface rust and turns brown over time, especially after being exposed to heat
  • Once browned, 409 grade steel cannot be polished and returned to its original finish

The below image taken by mcarmel shows the extensive rust on this 409 grade exhaust system.


It’s pretty clear that the properties of 304 grade steel mean it’s streets ahead of 409 grade in terms of strength, longevity and appearance. The strong anti-rust properties of 304 grade steel also make it the perfect choice of material for vehicle owners who live by the coast, tackle water crossings, or back their vehicle into water to unload a boat.

Interestingly, even 409 grade steel exhausts commonly use 304 in the small components such as exhaust tips, flanges and bolts, to guarantee strength. Torqit’s commitment to quality is reflected in the exclusive use of 304 grade stainless steel across the entire system, from the pipe through to all componentry such as nuts, bolts, flanges and brackets. For an exhaust which will likely outlive your vehicle, a 304 grade system backed by a 10 year product warranty will give you complete peace of mind.

So despite being more expensive, using 304 grade steel means an exhaust will deliver on both performance and longevity. Not to mention, you can go hard off-road and know that with a quick clean and polish, that piece of stainless out the back will look the same as the day you bought it.

Select the make and model of your 4WD to find out more on how a quality 304 grade exhaust can change the performance of your vehicle.