Episode 2: OEM vs Non-OEM Parts Explained: Key Differences Manufacturers See

OEM and Non-OEM parts may look the same—but do they really perform the same?

In this episode of Beyond Compression, host Pam Wasielewski sits down with Dave Sleeman, a seasoned service expert, to break down one of the most common—and costly—assumptions in industrial maintenance: that OEM and non-OEM parts are interchangeable.

From reverse engineering and material selection to micron ratings, tolerances, and long-term performance, this conversation pulls back the curtain on what manufacturers see that others don’t. Dave shares real-world field experience, including a case where a seemingly harmless non-OEM air filter led to reduced efficiency, vibration alarms, impeller damage, and nearly $50,000 in unplanned costs.

In this episode, you’ll learn:

• Why “looks the same” doesn’t mean “performs the same.”
• What’s lost when parts are reverse-engineered without original design data
• How non-OEM components contribute to early-life failures
• The hidden costs of downtime, efficiency loss, and secondary damage
• What OEM parts protect beyond performance—warranty, safety, and compliance

If you’ve ever considered saving a few dollars on replacement parts, this episode explains why the real cost often shows up later.

👉 Full case study:
https://www.fs-elliott.com/blog/oem-vs-non-oem-parts-explained-what-manufacturers-see-that-others-dont

Follow Beyond Compression on LinkedIn and Facebook for more insights from our engineering and service teams, and join us as we explore smarter, cleaner, more reliable compressed air systems.

Transcript

SPEAKER_01 0:09

Hello everyone and welcome back to Beyond Compression, the podcast where we share ideas, stories, and best practices around centrifugal air and gas compressor technology. Each episode will bring you insights from the people helping to shape the future of our industry. I'm Pam Wasileski, your host for today's episode, and today we're focusing on something that might seem small on the surface, but can have big consequences. We're talking about the differences between OEM and non-OEM parts. If you've ever looked at a replacement part and thought, it looks the same, why not try to save a few dollars? Famous last words, right? Then this episode is for you. Joining me today is Dave Sleeman, one of our seasoned service pros who has seen firsthand what happens when the wrong part ends up in the wrong machine. Thanks for joining us today, Dave.

SPEAKER_00 0:56

Thanks, Pam. I'm glad to be here. And you're absolutely right. In the field, the things that seem harmless or low risk can really cause the most damage.

SPEAKER_01 1:05

So let's start simple. When people hear aftermarket or non-OEM parts, what do they usually think?

SPEAKER_00 1:11

Yeah, so most people assume OEM and non-OEM is basically the same thing, just cheaper, since it looks the same and it appears to fit in the machine. And on the surface, they probably feel like it's a smart cost savings choice. And honestly, I get why people think that.

SPEAKER_01 1:28

Right? Especially when budgets are tight.

SPEAKER_00 1:31

Exactly. The issue is that in high performance equipment, looking the same and performing the same are two very different things. A machine doesn't care how a part looks, it cares how it behaves under load, heat, speed, and time.

SPEAKER_01 1:46

One thing that comes up a lot is reverse engineering. Can you explain what that really means?

SPEAKER_00 1:51

What reverse engineering means is that non-OEM manufacturers don't have access to the original engineering drawings, so they can't get material specs or performance data. And to get around that, they'll buy an OEM part, disassemble it, and measure it, and try to recreate it.

SPEAKER_01 2:07

It's like rebuilding a house by measuring the outside without knowing what's behind the walls.

SPEAKER_00 2:12

Yeah, and what usually gets lost is the why behind the design. Why a certain material was chosen, why a tolerance is that tight, and also why the surface finish actually matters. You can measure a finished part all day long, but you're not going to see those design decisions on a caliper.

SPEAKER_01 2:28

So you can end up with something that's close, but not close enough.

SPEAKER_00 2:32

And in rotating or high-speed equipment, issues with almost right add up fast.

SPEAKER_01 2:36

Now let's talk about cost, because that's usually the driver. What do you see when customers choose non-OEM parts to save money?

SPEAKER_00 2:45

Well, the upfront price looks good, but the real cost shows up later. We often see non-OEM parts fail just outside the expected service interval when nobody is expecting a problem. And based on inspections we've done, non-OEM components show up disproportionately in early life failures, often within the first 12 to 18 months, and the failure itself is only part of the cost. You're dealing with unexpected downtime, production losses, emergency repairs, and sometimes secondary damage. So you can see that the savings disappear pretty quickly.

SPEAKER_01 3:20

And warranty comes up a lot in these conversations. What should people really understand there?

SPEAKER_00 3:26

OEMs can only warranty equipment that's maintained using parts designed and validated to original specifications. So if a non-OEM part contributes to a failure, warranty coverage can be at risk. Beyond that, there's also safety and compliance, especially in regulated industries like semiconductors, pharmaceuticals, or food and beverage. Parts that haven't gone through the same validation process can introduce risks for these industries that go far beyond maintenance costs.

SPEAKER_01 3:56

So, before we wrap up today, can you share a time you ran into a non-OEM related failure in the field?

SPEAKER_00 4:02

Yeah, I've got one. And this started as pretty routine maintenance. The machine was already scheduled for downtime. Everything was locked out properly, and the customer was doing what they do every year, just replacing the air filter. However, instead of ordering the OEM air filter, they went with a third-party option. And to be clear, this wasn't careless. They were trying to be responsible with their budget. The filter visually looked the same, fit in the housing, and appeared interchangeable. But internally it wasn't.

SPEAKER_01 4:32

And is that where the issue started?

SPEAKER_00 4:35

Yeah, and it actually came down to the micron rating. OEM filters are designed with a specific micron rating that matches the machine's requirements. That rating determines what size particles get trapped and which ones are allowed to pass through the system. And in this case, the third-party filter didn't meet that rating. And it wasn't just the rating. The material density and the way the fibers were layered weren't equivalent to the OEM version either. So instead of stopping the microscopic contaminants it was supposed to catch, the filter let more of those particles through. You can't see them, but the machine absolutely can, and then those particles end up in places they don't belong. And after that, once they enter the airflow path, they kick off a slow chain reaction that starts affecting performance and reliability over time.

SPEAKER_01 5:24

And slow is an important word there. I'm assuming this doesn't happen overnight, does it?

SPEAKER_00 5:29

No, it took a while, actually. These aren't instant failures. You don't put the new filter in, and suddenly alarms start blasting. What happens is those tiny particles start piling up in spots they were never meant to reach. And over time, that buildup worked its way into the impeller assembly. And on a machine that's spinning that fast, it doesn't take much. Once things are even a little out of whack, the machine stops running where it should, and that's when it starts showing up in the data.

SPEAKER_01 5:56

And how did the plant discover there was an issue?

SPEAKER_00 5:59

The operator started to notice the machine wasn't performing quite like it normally did. The efficiency dipped 3% at first, which was just subtle enough that the operator chalked it up to changes in conditions or changes in load. But then the drop increased to 5%, and that's when it became clear something mechanical was going on. At the same time, vibration alarms were tripping occasionally, nothing catastrophic, but enough to raise an eyebrow. Eventually the customer called us because they could tell something wasn't right, but they couldn't pinpoint what was going on. Once we inspected the compressor, we found that the impeller had been damaged, not destroyed, not shattered, but damaged in a way that affected balance and performance. And at that point multiple components had to be replaced, not just the air filter. The cost wasn't just the replacement parts. It was also the labor costs and the time the machine was offline, also the work needed to get everything restored, and finally, the process of bringing the system back to proper operating conditions. Everything always adds up quickly. So that initial savings of around$300 for a cheaper filter ended up costing them close to$50,000 in the end.

SPEAKER_01 7:10

And that's the frustrating part. It's not like they were trying to cut corners. They thought the filter would work because on the outside it looked the same.

SPEAKER_00 7:18

Exactly. And that's why this topic matters. The issue isn't that customers are being careless, it's that the parts look deceptively similar. You can line them up side by side, and the average person can't tell them apart. But inside that filter and the material makeup, the layering of it, its density, and the performance rating, that's where the risk lies.

SPEAKER_01 7:39

So how often do you really run into this?

SPEAKER_00 7:41

Honestly, more often than I'd like. Which is exactly why I wanted to talk about this today. Filters, seals, oil, and o-rings are the big four. They're the most commonly replaced parts and therefore the most commonly substituted with non-OEM versions. And when the wrong material or rating is used, the machine always tells you. Maybe not in an hour, maybe not in a week, but eventually the machine exposes the weakness. And once the compressor is outside its ideal operating tolerances, the risk increases every hour it's running.

SPEAKER_01 8:17

Well, Dave, thanks again for taking the time to walk us through all of this. Really appreciate it. And to our listeners, thanks for joining us on another episode of Beyond Compression, an FS Elliott University podcast. If you'd like to dive deeper into the case we discussed today, the full write up is linked in the show notes. Be sure to follow us on LinkedIn and Facebook for more episodes, product updates, and insights from our engineering and service teams. And until next time, thanks for listening and for letting us be part of your journey towards smarter, cleaner, more reliable compressed air systems.