OEM parts are made by the original vehicle manufacturer and match factory fit and specifications exactly. Aftermarket parts cost less but are made by third parties and may vary in quality. California law requires insurers to disclose when aftermarket parts are used and gives owners of newer vehicles the right to request OEM parts.
OEM vs aftermarket parts is one of the most common debates in collision repair — and one your insurer will likely try to settle in their favor. Here’s what the difference actually means for your repair, your warranty, and your vehicle’s safety systems.
What OEM and aftermarket mean
OEM (Original Equipment Manufacturer) parts are made by the same manufacturer that built your vehicle — or by the exact supplier that provided parts to the factory. They are identical to the parts that came on your car. When you replace a Honda hood with a Honda OEM hood, you’re getting a part built to the same specification as the original.
Aftermarket parts are manufactured by third-party companies. Quality varies significantly — some aftermarket parts are excellent and some are poor fits that require modification to install. The insurance industry uses aftermarket parts primarily because they cost less, which directly reduces the insurer’s payout on your claim.
Where the OEM vs aftermarket parts debate matters most
For purely cosmetic parts on older vehicles — a fender, a door skin, a bumper cover — a quality aftermarket part from a reputable supplier often performs comparably to OEM at meaningfully lower cost. The fit may require minor adjustment, but an experienced shop can make it work.
For structural components, safety systems, and ADAS-related parts, the OEM vs aftermarket parts question has much higher stakes:
- Structural components — Crumple zones, side-impact beams, and pillar reinforcements are engineered to specific yield strengths and deformation sequences. An aftermarket structural part may not perform identically in a future collision.
- Airbag components — Anything related to airbag deployment — sensors, inflators, mounting brackets — should be OEM. Aftermarket airbag components have caused documented deployment failures.
- ADAS sensor mounts and housings — Cameras, radar units, and lidar sensors require precise mounting tolerances. An aftermarket bracket that’s off by a millimeter can make ADAS calibration impossible or produce inaccurate results.
- Windshields — On vehicles with forward cameras mounted to the windshield (most 2018+ vehicles), aftermarket glass with different thickness or optical properties can affect camera calibration.
What California law says about OEM vs aftermarket parts
California Insurance Code §758.5 requires insurers to use OEM parts on vehicles that are three model years old or newer — unless you consent in writing to alternatives. For older vehicles, the insurer can specify aftermarket parts, but they must inform you. You can elect to pay the cost difference to get OEM parts on any vehicle, regardless of age.
Some manufacturer-certified repair programs also require OEM parts regardless of vehicle age as a condition of maintaining certification. A shop with OEM certifications (Toyota, Honda, Ford, etc.) will advocate for OEM parts because their certification depends on it.
The insurer’s position and how to respond
Insurers default to aftermarket parts on older vehicles because it reduces their payout. When a shop requests OEM parts and the insurer declines, the shop can document the technical justification (ADAS compatibility, structural integrity, manufacturer repair procedure requirement) and submit a supplement. Not all supplements are approved, but a well-documented request citing specific OEM procedure requirements has a strong basis.
If OEM parts matter to you — particularly on a newer vehicle or one with ADAS features — tell the shop before the estimate is written. A good shop will note your preference, identify which parts are OEM-critical for your specific vehicle, and handle the insurer discussion on your behalf.
Our parts policy at Accent Collision
At Accent Collision, we follow OEM repair procedures for every vehicle. For structural components, ADAS-related parts, and safety systems, we specify OEM parts in our estimates and document the technical justification when insurers push back. For cosmetic parts on older vehicles where aftermarket quality is acceptable, we’ll tell you the trade-offs and let you decide. Our I-CAR Gold Class certification requires us to follow manufacturer repair procedures — and those procedures specify OEM parts for anything that affects safety.
Frequently asked questions
Does using aftermarket parts void my warranty?
On a new vehicle, aftermarket parts on a collision repair do not automatically void your factory warranty under the Magnuson-Moss Warranty Act. However, if an aftermarket part causes a failure, the manufacturer may not cover it. OEM parts avoid this ambiguity entirely.
Are “OEM equivalent” aftermarket parts as good as OEM?
The term “OEM equivalent” is marketing language with no legal definition. Some aftermarket parts are genuinely high quality; others are not. The only way to get a part you know was built to factory specification is to get an actual OEM part.
Can I require OEM parts on my 5-year-old car?
You can request them and pay the difference above the insurer’s aftermarket allowance. On ADAS-critical components, a well-documented supplement request citing OEM procedure requirements may get insurer approval for OEM at no cost to you.
Get a transparent estimate that specifies parts by type
Contact Accent Collision for a free written estimate — we’ll identify which parts are OEM-critical for your vehicle, explain the insurer’s position, and give you a clear picture of your options. Call (818) 788-8017.