When replacing auto parts on your automobile, you typically have the choice to either purchase parts directly from a dealership or from an outside supplier. Suppliers beyond a dealership will typically offer more than one version of a part in regards to where or how it was manufactured. Many people choose to purchase their parts from a local mechanic or from another retailer. These other sources sell the same parts that the dealer offers at a much lower price. A dealer will normally offer replacement parts that are the same part that came with the vehicle from the factory, before the car entered the showroom. These factory original parts are known as the OEM, or "original equipment manufacturer" part. While most other suppliers tend to carry OEM auto parts, they also do offer the same part not from the original manufacturer. These parts are referred to as aftermarket car parts.

Original manufacturer parts, commonly referred to as OEM car parts, are the parts that originally come with a vehicle when it is bought new at a car dealership. In most cases, these parts are not manufactured by the actual auto company. Instead, they are manufactured by a company specializing in that specific type of part. The auto company (ie: Honda) then re-packages that part so it can be sold at dealerships and associated with the car brand as its official part. Car dealerships will normally sell these OEM parts at very high prices. Previously, this was because dealerships were the only ones with access to the supply. However, OEMs are now supplying retailers and wholesalers the same exact parts.

Aftermarket parts are car parts that are made available to the public after a car is officially available and being sold through car dealerships. Aftermarket parts are typically an exact replica of the OEM part. In fact, it is very hard to differentiate aftermarket and OEM parts side by side. They normally fit and operate on a vehicle in the exact same way. Aftermarket parts are usually less expensive to purchase and in some cases, are an even better option than the OEM because they can correct some of the issues of OEMs.

Sometimes it is a very hard decision on which type of part to purchase for your car. Consumers can feel pressure from the car dealership to purchase "their part" or the OEM, because it is the original part for your car. However, it may in fact be better to purchase an aftermarket part for your vehicle as it will be exactly the same as the OEM at a cheaper price. More so, some aftermarket parts are a better option for your vehicle because they are the improved version of what the car dealership originally offered with your vehicle at the dealership. They are also always the cheaper option.