What is OEM? | Revv.ly Car Culture Glossary

What is OEM?

After thirty-odd years of buying, owning, and occasionally selling cars, I've come to appreciate something that younger enthusiasts often overlook: there's genuine value in keeping things original. OEM--Original Equipment Manufacturer--refers to parts and specifications as they left the factory. And while the modification world celebrates changing everything, there's wisdom in understanding what you're changing from.
OEM parts are manufactured to the specifications set by the vehicle manufacturer, either produced by them directly or by authorized suppliers. When you buy an OEM brake rotor for your BMW, you're getting the same part that was fitted at the factory in Munich. Not "equivalent," not "compatible"--the same.

The Case for Original

There are compelling reasons to value OEM:
Engineering Integration -- Factory parts were designed as part of a complete system. The suspension bushings were chosen to work with the spring rates, which were tuned for the weight distribution, which considered the tire size. Changing one element affects others in ways that aftermarket parts may not account for.
Quality Consistency -- OEM parts meet manufacturer specifications. They fit correctly, perform to known standards, and have been validated through the vehicle's development process. Aftermarket parts vary wildly in quality.
Documentation and Support -- Factory part numbers, service intervals, and procedures are based on OEM specifications. Deviating from them means navigating without the roadmap.
Resale Value -- For collector vehicles especially, originality matters. A matching-numbers car with factory specifications commands premiums that modified examples rarely achieve.

When OEM Makes Sense

I'm not arguing against modification--I've modified plenty of vehicles myself. But there are situations where OEM is clearly preferable:
Wear Items on Daily Drivers -- Brake pads, filters, fluids, and similar consumables. The factory figured out what works; reinventing the wheel (so to speak) offers little benefit.
Collector and Investment Vehicles -- If long-term value matters, maintain originality. Even if you plan to modify, keep the original parts for potential restoration.
Unknown Applications -- When you don't know what to choose, OEM is a safe default. It was good enough for the factory's engineers.
Maintaining Factory Warranties -- Using non-OEM parts can complicate warranty claims, even if the part isn't directly related to the failure.

OEM vs. OE vs. Aftermarket

Terminology matters:
OEM (Original Equipment Manufacturer) -- The company that made the original part. For brake pads, this might be Brembo, Akebono, or another supplier who provided the factory parts.
OE (Original Equipment) -- The actual part as fitted to the vehicle. Sometimes used interchangeably with OEM.
OE-Spec -- Aftermarket parts claiming to meet OEM specifications. Quality varies; some are excellent, others are marketing fiction.
Genuine Parts -- Parts sold through the vehicle manufacturer's parts department, carrying their branding. These are usually OEM parts with the manufacturer's markup.

The Middle Path

In practice, most enthusiasts blend OEM and aftermarket. Factory maintenance items where they excel, aftermarket where they offer genuine improvements, and careful evaluation of quality in either case.
What I've learned over the years: respect what the factory engineers accomplished before changing it. Understand why they made their choices. Then modify intentionally rather than randomly.
The Revvly community includes collectors who value originality alongside modifiers who appreciate what they're working with.
Related: OEM Plus, Preventive Maintenance, Daily Driver
Marques Where OEM Matters Most: Porsche 911, BMW M3, Honda S2000