OEM vs. Aftermarket Parts: What Actually Goes On Your Car
Short answer: your insurer can specify parts your car's manufacturer did not make, and in most states its duty is to tell you so in writing. The four part types differ in fit, in warranty, and in who stands behind them.
Every collision estimate quietly answers a question most owners never see asked: which kind of parts? The answer affects fit, safety systems, resale paperwork, and sometimes your warranty, so it's worth two minutes to understand the menu.
The four part types
OEM (Original Equipment Manufacturer), made by or for your vehicle's manufacturer, identical to what the car was built with. Best fit and finish, required for some structural and safety-adjacent repairs under manufacturer procedures, and the most expensive of the four.
Aftermarket: made by third parties to imitate the OEM part. Quality ranges from excellent to poor. The credible tier carries CAPA certification (an independent testing body for cosmetic parts like bumper covers, fenders, and lamps); uncertified aftermarket is the wild west.
Recycled (used/LKQ): genuine OEM parts pulled from salvage vehicles. For bolt-on components like doors, hoods, and wheels, a clean recycled OEM part is often better than a new aftermarket copy: factory metal, factory fit, lower price.
Remanufactured: used components rebuilt to spec, common for wheels, lamps, and mechanical parts.
What the manufacturers themselves publish
What your policy allows and what your car's manufacturer says are two different questions, and the manufacturers do not answer theirs the same way as each other. We read every published parts position statement we could find and compared the seventeen of them side by side. One uses the word prohibits. Most use a weaker verb. Several name only aftermarket parts and say nothing at all about a recycled door, which leaves that question unaddressed rather than settled.
Wheels are their own argument and they have their own documents. Sixteen manufacturers publish a position on repairing one, and every one of the sixteen draws the same line in a different place: you may sand a wheel and repaint it, you may not straighten, weld, heat or machine it. If a reconditioned wheel is on your estimate, that is the page to read before the argument starts.
Salvage and recycled parts are a third question again, and the surprise there is the filing rather than the positions. The library lists fifteen entries under salvage parts and only nine of them are documents written about salvage. Six are general parts statements filed under the heading as well, and two of those never mention a salvage part anywhere.
Where the fight usually happens
Insurance policies commonly authorize "like kind and quality" parts, which in practice means aftermarket or recycled on cosmetic panels for out-of-warranty vehicles. Several states require the insurer to disclose aftermarket use on the estimate, and some require your consent or an OEM option for newer vehicles. Your leverage: read the estimate line by line (every part is labeled (OEM, A/M, LKQ, Recond)), and ask questions before work begins, not at pickup.
Where part choice genuinely matters for safety
Modern vehicles are engineered systems, not collections of panels. Three places to insist on manufacturer procedures and appropriate parts:
- Structural components: rails, aprons, pillars. Manufacturer repair procedures often specify OEM parts and exact sectioning locations; deviating can change how the car absorbs the next crash.
- Anything a sensor looks through or mounts to: windshields, bumper covers, emblems, grilles. Radar and camera systems are calibrated to OEM optical and material properties; a bargain windshield can make a safety system see the world wrong. (More in our ADAS calibration guide.)
- Airbag and restraint components, new OEM only, no exceptions worth discussing. That is not just our view: not one of the twelve manufacturer entries we read on airbags approves a used restraint component, and two of them tell the installer they may be breaking federal law.
In one state, following the procedure is not optional
Most of this argument happens in the space between what a manufacturer publishes and what an insurer will pay for. Nevada closed part of that space by statute.
NRS 487.688: "If a body shop or garage performs repairs on a motor vehicle, the body shop or garage shall perform the repairs in accordance with any specifications of the manufacturer of the motor vehicle and the written estimate or statement of the cost of the repairs that is most recently agreed upon."
Note what it does and does not do. It requires the procedure to be followed. It does not require OEM parts: Nevada elsewhere contemplates aftermarket and used parts openly, and its own salvage-title calculation at NRS 487.890 lets a repair estimate be built on "the current published actual retail price of original manufacturer equipment, retail price of new alternative equipment or the actual cost of used parts."
So Nevada separates the two questions this guide separates: which part is a commercial choice, how it goes on is a legal duty. That is a useful frame even outside Nevada, because it is the distinction a good shop is already making when it explains a mixed-parts estimate.
We found this while reading Nevada's salvage law for another reason, and we have not checked the other fifty jurisdictions for an equivalent. It is the only one we have found, which is not the same as the only one there is.
California decided what your estimate is allowed to call a part
If you have ever looked at an estimate line reading "Opt OEM" or "Alt OEM" and wondered what it actually means, so did California's regulator. In 2018 the Department of Insurance issued a formal legal opinion to the California Autobody Association answering that and two related questions. It is worth reading because it goes further than any consumer explainer will.
The terminology finding. The Department's reasoning is that terms like these "do not have generally accepted meanings or definitions," and that using them "arguably implies incorrectly that used, blemished, or returned OEM parts or non-OEM parts are new OEM parts." Its conclusion is not hedged:
"if an insurer uses any designation or describes any replacement part as anything other than OEM or non-OEM, such as 'Optional OEM,' 'Alternate OEM' or 'Surplus OEM', the use of such terms would constitute a violation of the California Unfair Practices Act."
Two categories, in California. OEM, or non-OEM. Everything else is a marketing word on a legal document.
The steering finding, which is the bigger one. The association had also reported insurers refusing to pay more for a part than the price quoted by the insurer's own preferred vendors, while denying they required shops to buy there. The Department treated that as the same problem as steering you to a shop. No insurer may require a vehicle be repaired at a specific shop, and where a claimant picks their own, the insurer "may not limit or discount the reasonable repair costs based on charges that would have been incurred had the vehicle been repaired by the insurer's preferred shop." Capping a part at a preferred vendor's price, the opinion reasons, does exactly that, "thereby preventing customers from using the repair shop of their choice."
And the lever the insurer keeps. The same opinion is careful about what it does not take away: an insurer "would, however, be permitted to reasonably adjust a collision repair shop's written parts price estimate for any part, including new OEM crash parts, if the insurer demonstrates that the price charged by the repair shop for the replacement part is 'unreasonable.'" Note where the burden sits in that sentence. The insurer demonstrates it.
What the rule itself requires when non-OEM parts are specified. Separately, California's fair claims regulation sets five conditions before an insurer may require non-OEM crash parts. They must be "at least equal to the original equipment manufacturer parts in terms of kind, quality, safety, fit, and performance"; the insurer "shall pay the cost of any modifications to the parts which may become necessary to effect the repair"; the insurer must "warrant" the parts are of like kind, quality, safety, fit and performance; the parts must carry "sufficient permanent, non-removable identification so as to identify the manufacturer," accessible so far as possible after installation; and the use must be disclosed under the Business and Professions Code.
The Department has enforced the identification condition specifically, telling insurers they may not require a shop to install such a part, or limit payment to its cost, unless it carries that permanent marking. In the same notice it flagged that "certain aftermarket bumper reinforcement bars may be significantly different in terms of like kind, quality, safety, fit, and performance as compared to the original equipment manufacturer replacement part." A regulator naming a part category is rare enough to be worth remembering.
The honest limits. This is California, and it binds insurers admitted there. A legal opinion is the Department's interpretation, issued under its opinion authority, not a statute or a court ruling, and the reasoning uses "arguably" even where the conclusion does not. The Department also expressly declined to take a position on whether the parts-price differentials raised with it violate the federal Robinson-Patman Act, saying that is outside its jurisdiction. None of it makes a part choice illegal by itself. What it does is tell you, in a regulator's own words, that the words on your estimate are not a free-form field.
What this means for your estimate
A mixed-parts repair is normal and often sensible: recycled OEM door, CAPA-certified bumper cover, new OEM structural bracket. What you're checking for is deliberateness, a shop that can explain each part choice against the manufacturer's repair procedures is doing engineering; a shop that just takes whatever the estimate platform spits out is doing arithmetic.
Questions worth asking your shop
Which parts on this estimate are non-OEM, and why those? Will any part choice affect my manufacturer warranty or lease return? Are you following the manufacturer's published repair procedures for the structural work? Do you warranty the parts and the labor separately?
The records angle
Part choice is also about who's holding the wrench. Manufacturer certification programs (Tesla, Ford aluminum, BMW, and the rest) exist because some repairs require specific training, tooling, and parts discipline. A shop's certifications, along with its state license and compliance history, are public, verifiable facts, and that's what this directory checks, so "we're certified" is something you can confirm rather than take on faith.
Sources
- California Department of Insurance, legal opinion "Insurer Designations Involving Original Equipment Manufacturer (OEM) Parts", issued 8 October 2018 to the California Autobody Association under Cal. Ins. Code 12921.9, read in full on 2026-08-15. The parts-terminology holding, the preferred-vendor steering analysis under Cal. Ins. Code 758.5, the "unreasonable price" adjustment the insurer retains under 10 CCR 2695.8(f), and the Department's declining of the Robinson-Patman question all come from that document.
- California Department of Insurance notice, "CCR 2695.8(g), Use of Non-Original Equipment Manufacturer Replacement Crash Parts", 29 April 2010, read in full on 2026-08-15, for the five conditions in 2695.8(g), the permanent-identification enforcement position, and the bumper reinforcement bar warning.
- Nevada: NRS 487.688 and NRS 487.890, read first-party and recorded in our salvage register.
One note on method. The 2018 opinion is published as a scanned PDF whose text layer breaks words across lines and misreads some section numbers. Quotations above were transcribed from that layer and the statute and regulation numbers written out in full from the citations themselves; where a passage could not be read cleanly it is described rather than quoted.
General consumer information: not legal, insurance, or financial advice. Requirements, coverage, and practices vary by state, policy, and manufacturer.
Where this fits
Each link says what it is for. We add one only when a reader on this page has a real reason to need that page next.
- Your State's Aftermarket Parts Law Almost Certainly Does Not Cover Your Windshield (the exception that surprises people: glass is usually carved out)
- When Insurance Won't Pay for a Proper Repair: ADAS, OEM Procedures, and Your Options (what to do when the parts choice is the disagreement)
- Structural vs Cosmetic Damage: What Changes When the Damage Goes Deeper (where the part sits on the car decides how much the choice matters)
- Can You Read Your Car's Repair Manual? We Tried Seven Doors. (whether the manufacturer standard behind this argument is one you can look up yourself)
- Who Governs the Certifier Behind Your Certified Parts (If the answer to the aftermarket question is "but it is certified", this is who does the certifying and who checks them.)
- Who Pays to Take a Counterfeit Airbag Out of Your Car (The failure case for a non-OEM part, where the part is counterfeit, there is no recall, and the owner pays to remove it.)