Not sure how to tell the difference between an OEM and aftermarket catalytic converter? You’re not alone. Many auto repair shops struggle with this — and it’s costing them real money. 

In this episode of Noble6 Talks, Ed and Rich break down the key visual cues, markings, and metal load differences that can help you confidently identify what you’re working with, so you don’t accidentally sell high-value units at low-value prices. 

 

Why OEM Converters Are Worth More 

The primary reason OEM converters are worth significantly more is simple: they contain more precious metal. 

• OEM converters are built to meet long-term EPA standards 

• They’re designed to last 7–15 years, sometimes for the entire life of the car 

• Aftermarket converters, on the other hand, are often short-term replacements and contain far fewer PGMs 

As Ed puts it: you could have an OEM converter worth $300–$500, or an aftermarket one worth just $10. Learning the difference is the first step to maximizing your profits. 

 

Key Signs You’re Looking at an Aftermarket Converter 

Here are some visual and structural clues Ed and Rich point out: 

• 45° weld seams where the shell was assembled 

• Flow arrows (with or without the word “flow”) 

• Poor welding craftsmanship  

• Yellow or banana-colored monolith inside (vs. OEM’s dark gray) 

• Square or rectangular aftermarket tags — or signs they were removed 

If it looks like a duck and quacks like a duck… it’s probably aftermarket. 

 

What to Look for in an OEM Converter 

OEM converters usually include: 

• Manufacturer logos (e.g., Toyota, BMW, GM) 

• Letter-number combos like GD3, EA2, 5G232FC, 55567024 etc. 

• Clean, factory-grade welds 

• Dark gray monolith visible inside the case 

The higher craftsmanship and clearly marked part numbers are big tells. And once you know what to look for, it becomes second nature. 

 

Why It Pays to Know the Difference 

Let’s say a road buyer comes into your shop and tries to sort your pile of converters — “these are aftermarket, these are OEM.” If you don’t know the difference, you can’t call out bad sorting or recognize when someone’s trying to buy an OEM unit for aftermarket pricing. 

But when you’re confident in what you have, you can: 

• Negotiate from a position of strength 

• Avoid being misled 

• Hold buyers accountable 

That’s how you protect your bottom line. 

 

Use a Flashlight, Use the App — Use Your Tools 

When in doubt, Ed and Rich suggest: 

• Grabbing a flashlight and checking monolith color 

• Comparing weld quality 

• Using the noble6 Price Guide to verify part numbers and values 

If it’s rusted, unreadable, or borderline, stack your clues — if two or three indicators point to aftermarket, it probably is. 

 

Stop Guessing, Start Profiting 

Every time you guess, you risk leaving money on the table. Use a price guide that: 

• Allows you to search by part number 

• Helps you distinguish foil, ceramic, and diesel 

• Makes OEM vs. aftermarket obvious 

 

Still Not Sure What You Have? 

Reach out to the Noble6 team. Send pictures. Share make, model, and year.
Our team helps shops across the country identify converters accurately and honestly — so you get what you deserve. 

And remember: 

You’re just one converter away from making the right call — and increasing profits.