What you need before you order a car part online
Ordering the wrong part online wastes money and time, so you need three pieces of information before you click buy: your vehicle's year, make, model, and engine size. Some sites ask for your VIN (vehicle identification number) instead, which is faster and more accurate. Your VIN is on your registration, insurance card, or the dashboard on the driver's side where it meets the windshield.
The part number matters as much as the vehicle details. If you already know what part you need — say, a water pump or alternator — write down the part number from your current part, a repair estimate, or your vehicle's manual. When you search online, use both the part name and the number. A search for "water pump" alone might return 50 results; a search for "water pump 16100-22010" returns the exact part for your engine.
Check the seller's return policy before you pay. Most online retailers let you return unused parts within 30 days, but some charge a restocking fee or require you to pay return shipping. A few do not accept returns at all. If the part arrives damaged or wrong, the seller should cover the return cost — but read their policy to confirm.
Key Takeaways
- Have your vehicle's year, make, model, and engine size or VIN ready before you search, because the same part name fits dozens of different vehicles.
- Use the part number along with the part name when you search online, because it narrows results to the exact item your engine needs.
- Read the return policy before you order, especially whether the seller charges restocking fees or requires you to pay for return shipping.
- OEM parts come directly from your vehicle's manufacturer and fit with no modification, while aftermarket parts are made by other companies and may vary in quality and fit.
- Shipping times vary widely — some retailers ship same-day, others take a week or more, so check the estimated delivery date before you order if you need the part urgently.
OEM versus aftermarket parts and what the difference costs
OEM (original equipment manufacturer) parts are made by the company that built your vehicle. Ford makes Ford parts, Toyota makes Toyota parts, and so on. These parts are engineered to fit your specific model year and usually come with a warranty. The trade-off is cost — OEM parts are typically 20 to 40 percent more expensive than aftermarket alternatives.
Aftermarket parts are made by other manufacturers — companies like Dorman, Motorcraft (which is actually Ford's parts brand but sold separately), or dozens of smaller suppliers. Aftermarket parts fit most vehicles in a category but may not match your exact model as closely as OEM parts do. Quality varies widely. Some aftermarket parts are nearly identical to OEM and cost much less; others are cheaper because they use lower-grade materials or looser tolerances.
For wear items like brake pads, air filters, or wiper blades, many drivers choose aftermarket because the difference in performance is small and the savings are real. For engine or transmission components, many prefer OEM because the fit is may provide and the warranty is longer. Your repair estimate or vehicle manual often recommends one or the other, or lists both with the price difference so you can decide.
How to search and compare prices across different retailers
Start with the retailer your mechanic or dealership uses, because they often have volume discounts and can answer questions about fit. Major online retailers include RockAuto, Amazon, eBay Motors, Advance Auto Parts, AutoZone, and O'Reilly Auto Parts. Each has a parts search tool where you enter your vehicle information and the part name.
Once you find the part on one site, search for it on two or three others using the part number, not just the name. Prices vary significantly — the same alternator might cost $120 on one site and $180 on another. Factor in shipping cost and delivery time, because a cheaper part that takes two weeks to arrive may not save you money if you need it sooner.
Read the product description carefully. It should list what vehicle years and models the part fits, whether it is new or remanufactured, and what is included in the box. A remanufactured part is used, cleaned, and rebuilt to like-new condition — it costs less than new but usually comes with a shorter warranty. Check whether the part comes with gaskets, seals, or mounting hardware, because you may need to buy these separately.
Remanufactured, refurbished, and used parts — what the labels mean
A new part is unused and comes with the manufacturer's full warranty, usually one to three years depending on the part and maker.
A remanufactured part is used, disassembled, cleaned, inspected, and rebuilt to meet the original manufacturer's specifications. It is tested before sale and usually comes with a warranty of 12 to 24 months. Remanufactured parts cost 30 to 50 percent less than new and are reliable for most applications — many shops use them for alternators, starters, and transmissions.
A refurbished part is used, cleaned, and tested but not fully disassembled and rebuilt like a remanufactured part. The warranty is usually shorter — often 30 to 90 days. Refurbished parts are cheaper than remanufactured but carry more risk because you do not know how much wear the original part had.
A used part is pulled from a salvage vehicle, cleaned, and sold as-is with no warranty or a very short one. Used parts are the cheapest option but the riskiest — you have no way to know how long they will last. Some buyers use them for older vehicles where cost matters more than reliability, or as temporary fixes while saving for a new part.
Shipping, delivery times, and what to do if the part arrives damaged
Shipping costs and times vary widely. Some retailers offer free shipping on orders over a certain amount; others charge a flat fee or calculate it by weight and distance. Delivery times range from same-day or next-day (usually at a premium) to five to seven business days for standard shipping. Check the estimated delivery date before you order — if you need the part in two days and the site says five to seven, that retailer is not the right choice.
When the part arrives, inspect it before you sign for it if possible. Check that the part number on the box matches your order, that the box is not visibly damaged, and that the part itself is not cracked, dented, or missing pieces. If something is wrong, photograph it and contact the seller when ready — most will issue a replacement or refund without requiring you to return the damaged item first.
If the part is damaged in shipping, the seller is responsible for the replacement cost and return shipping. If you opened the box and installed the part before discovering damage, the seller may deny the claim, so inspect before you install. Keep the original box and packing material for at least 30 days in case you need to return the part.
Checking fitment and avoiding common ordering mistakes
The most common mistake is ordering a part for the wrong year or engine size. A 2015 Honda Civic and a 2016 Honda Civic may look identical but use different parts. A 2015 Civic with a 1.8-liter engine and a 2015 Civic with a 2.0-liter engine need different water pumps. Always enter your exact year, make, model, and engine size — not just "Honda Civic."
Some parts come in left-hand and right-hand versions. Door handles, mirrors, and some suspension components are different on the driver's side and passenger's side. The product description should specify which side the part is for. If it does not, contact the seller before you order.
Check whether the part requires installation tools or special knowledge. Some parts — like air filters or wiper blades — take five minutes to install. Others — like alternators or water pumps — require removing other components and may need a torque wrench or specialty tool. If you are not comfortable installing it yourself, budget for a mechanic's labor before you order the cheapest part you can find.
Warranty coverage and what to do if the part fails
New parts usually come with a manufacturer's warranty of one to three years, depending on the part type and maker. Remanufactured parts typically have a 12 to 24-month warranty. Refurbished and used parts may have no warranty or a 30 to 90-day warranty. The warranty covers defects in materials and workmanship, not damage from improper installation or accidents.
To claim a warranty, you usually need the original receipt and proof of purchase. Keep your order confirmation email and the packing slip that came with the part. If the part fails within the warranty period, contact the seller with your order number and a description of the failure. They will ask you to return the failed part before they send a replacement — some sellers waive this for parts under a certain price.
Warranty claims can take two to four weeks because the seller has to receive the failed part, inspect it, and verify that the failure was a manufacturing defect and not user error. If you need the part urgently, ask the seller whether they will send a replacement before receiving the failed part back — many will for repeat customers or high-value items.
Frequently Asked Questions
Is it safe to buy parts from sellers I have never heard of?
Check the seller's feedback rating and return policy first. On Amazon and eBay, look for sellers with 95 percent or higher ratings and at least 100 reviews. Read a few negative reviews to see whether complaints are about the part itself or the seller's service. If the seller has a clear return policy and good ratings, the risk is low — you can return the part if it does not fit.
Can I return a part if I ordered the wrong one by mistake?
Most retailers accept returns of unused parts within 30 days, but you may have to pay return shipping. Some charge a restocking fee of 10 to 20 percent. Check the return policy before you order. If you ordered the wrong part, contact the seller as soon as you realize the mistake — some will let you cancel the order before it ships and avoid return costs entirely.
What is the difference between a part number and a VIN?
A part number is a code specific to one component — for example, a water pump for a 2015 Honda Civic. A VIN is your vehicle's identification number, which tells the retailer your year, make, model, and engine size. Entering your VIN is faster and more accurate than typing all that information separately, but you still need the part name or number to find what you are looking for.
Should I buy OEM or aftermarket parts to keep my warranty valid?
Using aftermarket parts does not automatically void your vehicle's warranty. The manufacturer has to prove that the aftermarket part caused the failure of a covered component. For routine maintenance items like filters and brake pads, aftermarket parts are fine. For major components, check your warranty documentation or ask your dealership whether they recommend OEM parts for your specific situation.
How do I know if a part is compatible with my vehicle?
Enter your year, make, model, and engine size into the retailer's search tool, or provide your VIN. The search results should show only parts that fit your vehicle. If you are unsure about the engine size, check your vehicle's manual, registration, or ask your mechanic. When in doubt, call the retailer's customer service — they can confirm fitment before you order.