What Are OEM Parts?
OEM (Original Equipment Manufacturer) parts are made by the same company that supplied parts to the vehicle manufacturer. When you buy a door seal from a BMW dealer, it's an OEM part — usually branded with the BMW logo and carrying a premium price.
What Are Aftermarket Parts?
Aftermarket parts are made by third-party manufacturers. Quality varies hugely — from budget copies to premium alternatives manufactured to the same specifications as OEM parts.
Price Comparison
For a typical door weatherstrip seal: - **OEM (dealer price):** £80-£180 - **Quality aftermarket:** £25-£60 - **Budget aftermarket:** £10-£20
That's a significant price difference, but does cheaper mean worse?
Quality Comparison
Material - **OEM:** Always EPDM with metal reinforcement - **Quality aftermarket:** EPDM with metal reinforcement (same material) - **Budget aftermarket:** Often PVC or low-grade EPDM without reinforcement
Fitment - **OEM:** Perfect fit guaranteed - **Quality aftermarket:** Engineered to OEM specs, 95-99% fit accuracy - **Budget aftermarket:** Hit or miss, often requires trimming
Longevity - **OEM:** 10-15 years - **Quality aftermarket:** 8-12 years - **Budget aftermarket:** 2-4 years
Our Recommendation
For most vehicle owners, a **quality aftermarket seal** offers the best value. At Genuine Motors, our products are manufactured to OEM specifications by ISO 9001:2008 certified facilities. You get 90%+ of the OEM quality at 30-50% of the price.
The only scenario where we'd recommend OEM is for concours-level restorations where absolute originality matters.