Sooner or later every car owner is asked the same question at the service counter: "Genuine or local?" The answer changes the price of the job, sometimes by a lot, so it is worth understanding what you are actually choosing between before you say yes.
What the terms actually mean
OEM and genuine parts
OEM stands for Original Equipment Manufacturer. An OEM part is built to the carmaker's specification and is the same design that was fitted when the car was assembled. Genuine parts are OEM parts sold in the vehicle manufacturer's own packaging, usually through its dealer network.
OES: the middle ground
Many components are made by an outside supplier for the carmaker. When that same supplier sells the identical part under its own brand, it is often called OES (Original Equipment Supplier). It is essentially the OEM part without the carmaker's logo, and often costs less.
Aftermarket parts
Aftermarket parts are made by independent manufacturers to fit a range of vehicles. Some meet or exceed the original specification; others are built to a price. The category is huge, which is exactly why brand and specification matter so much.
OEM vs aftermarket, side by side
| Factor | OEM / genuine | Aftermarket |
|---|---|---|
| Fit and finish | Designed for your exact model, so fitment is predictable | Good brands fit well; budget ones may need adjustment |
| Price | Usually higher | Often noticeably lower, with more price tiers |
| Choice | One option per part | Many brands, grades and specifications |
| Quality consistency | Consistent | Varies widely by brand |
| Warranty | Typically backed by the carmaker | Depends on the manufacturer; always ask |
| Availability for older cars | Can be discontinued | Often easier to find |
When OEM is the safer choice
- Sensors, control modules and electronics. These are tuned to your car's software, and a slightly different part can trigger warning lights.
- Safety systems such as airbag components and seat-belt parts.
- Parts on a car still under warranty. Check the terms of your warranty and service booklet first.
- Precision engine and transmission internals where tolerances are tight.
When a good aftermarket part makes sense
- Regular wear items: oil filters, air filters, cabin filters, wiper blades and spark plugs.
- Older cars where the OEM part is expensive or no longer made.
- Upgrades such as better brake pads or performance suspension, where the goal is to improve on the original.
How to judge aftermarket quality
- Stick to recognisable brands. Established manufacturers publish specifications and stand behind them.
- Match the part number. A reputable listing shows the OEM number it replaces. See our guide on finding the right spare part.
- Ask about warranty. A manufacturer confident in its part will put it in writing.
- Be wary of unbranded parts priced far below everything else. If a brake pad costs a fraction of the rest, ask what was saved.
A practical rule of thumb
Spend on parts that keep you safe or that your car's electronics depend on. Save on parts that are simply replaced on a schedule, as long as you buy from a brand you can trust. SpareBlaze lists both OEM parts and aftermarket parts, so you can compare like for like before you decide.
