Mopar parts are the official parts and service brand for Chrysler, Dodge, Ram and Jeep vehicles, OEM parts are made to the original manufacturer’s specification, and aftermarket parts are made by other companies as alternatives, so the right choice depends on the part, the car and what you want from it.
The three terms get mixed up constantly, even by people who sell parts. Here is a clear way to tell them apart, and how to decide between them when you are repairing a Dodge, Ram or Jeep in the UK.
What Mopar actually means
Mopar is short for “MOtor PARts”. It began as a Chrysler parts business in the 1920s and became a well-known name over the following decades. Today it is owned by Stellantis, which has held it since 2021. It covers the Chrysler family of brands, including Chrysler, Dodge, Ram, Plymouth, Imperial, DeSoto, AMC, Eagle and Jeep. Importantly, Mopar is a parts and service brand, not a car brand. If you want the full story, see our guide to what Mopar is and where the name comes from.
What OEM means
OEM stands for “original equipment manufacturer”. In everyday use it means a part built to the same specification as the one fitted when the car was made. Here is where it gets confusing: a genuine Mopar part is usually OEM, but not every OEM part carries a Mopar box. Car makers buy components from specialist suppliers, and those suppliers sometimes sell the same part in their own packaging. That is still OEM in the sense of the original design and supplier, just without the vehicle maker’s branding.
What aftermarket means
Aftermarket parts are made by companies that are not the vehicle manufacturer. They range widely. Some copy the original design closely and aim to be a straight replacement. Others improve on it, such as upgraded brake pads or a freer-flowing exhaust. Others are simply built to a price. “Aftermarket” tells you who made the part, not how good it is.
Quality is not decided by the label
It is tempting to assume Mopar is always best and aftermarket is always worse. In practice it varies by part. Some aftermarket makers have long reputations and supply a great many cars. Equally, an old stock part can have aged badly on a shelf, particularly rubber, seals and anything with a shelf life. Our guide to NOS, OEM, reproduction and used parts explains how age and origin affect what you receive.
When genuine or OEM makes sense
- Restorations and show cars where originality matters.
- Electronic and sensor parts, where a small difference in specification can cause warning lights or odd behaviour.
- Fitment-critical items, such as body panels, trim and brackets, where an exact match saves hours of fettling.
- Anything you will find hard to access again, such as a gearbox or engine internal where labour is the main cost.
When aftermarket makes sense
- Wear items like filters, wipers, bulbs, spark plugs and standard brake pads, where there is plenty of competition and good choice.
- Upgrades, such as better cooling, brakes or suspension for a car that now works harder than it did originally.
- Older models where the original part is no longer made and a reproduction is the only practical route.
- Daily drivers on a budget, where a sensible, reputable alternative keeps the car on the road.
Safety-critical parts deserve extra care
For brakes, steering, suspension, tyres and towing equipment, choose from a supplier you trust, check that the part is correct for your exact vehicle, and have the work done or checked by a qualified person. This is not about being alarmist. It is simply that these parts do a job where a poor fit matters. Our brake parts buying guide goes into more detail, and you can browse our brakes category.
What this means when you buy
- Start with your VIN. The right part depends on the exact build of your car, and our VIN check helps you narrow it down.
- Ask what you are actually being sold: genuine, OEM-supplier, reproduction, new old stock or used.
- Match the part to the job. Restoring a show car and keeping a work truck running are different goals.
- If you cannot find what you need, use our Source a part form and we will help look for it.
- Keep the old part until the new one is fitted and working, so you can compare them side by side.
Frequently asked questions
Is Mopar the same as OEM?
Not quite. Mopar is the manufacturer’s parts brand, and its parts are generally OEM. But OEM is a wider term that can include the same components sold through the original supplier under a different name.
Will aftermarket parts affect my car’s value or reliability?
It depends on the part and the maker. Quality aftermarket parts fitted correctly are common on well-kept cars. On a concours restoration, originality usually matters more, so keep receipts and be clear about what has been fitted.
Can I fit parts myself, or should a garage do it?
Many jobs suit a competent home mechanic. For brakes, steering and suspension, or anything you are unsure about, get a qualified person to do or check the work. Oldcott Motors’ workshop can fit parts you have bought elsewhere.
Need a hand choosing between options for your Dodge, Ram or Jeep? The team at Oldcott Motors, an official Dodge and Ram dealer selling American cars since 1958, is happy to talk it through.