The 7-Point Vehicle Parts Checklist I Use Before Every Purchase Order

Who this checklist is for

I manage parts procurement for a 25-vehicle company fleet—mostly service vans and a handful of executive sedans. That means when somebody needs brake pads, a replacement radiator overflow cap, or a set of crankshaft parts, the request lands on my desk. I am not a mechanic. I am the person who has to make sure the right part shows up, the invoice clears finance, and nobody's vehicle sits in the shop an extra week because I ordered the wrong thing.

I built this checklist after my third ordering mistake in 2022. It has seven steps. Run through it every time, and you will avoid most of what I got wrong.

Step 1: Get the OEM part number before you get the description

When a driver or shop foreman tells me they need "front brake pads for the Transit," that is a description, not a part number. Descriptions get you close. Part numbers get you correct. I now require the OEM number on every request (or the VIN so I can look it up myself).

This matters even more for things like crankshaft parts, where the same engine family can have different bearing sizes across model years. A customer service rep once told me "they're all the same for that engine." They were not all the same. We returned two sets and ate a 15% restocking fee. That is a $340 lesson in why the OEM number goes in the email, not in a follow-up message three days later.

Step 2: Verify brake components against the spec sheet—not the marketing page

Brake parts are where I got lazy early on, because the brand names are familiar. I would search for raybestos or pull up a raybestos brake pad review and assume that was enough due diligence. It is not.

Product reviews tell you whether other buyers were happy. They do not tell you whether the part fits your vehicle's caliper bracket or matches the rotor thickness spec. For raybestos element 3 calipers, for example, the fitment charts are specific to year, make, model, and sometimes trim level. I now cross-check three things every time: the OEM interchange number, the caliper piston diameter, and the bracket configuration (if included).

Five minutes with the spec sheet on the supplier's site beats two weeks of a van being down because the caliper bolted on but the brake line fitting didn't match.

Step 3: Don't skip the small, cheap parts

The radiator overflow cap is a $6 part. It is also the reason one of our vans overheated on the interstate last spring. The cap had a cracked seal, coolant escaped under pressure, and the driver didn't notice until the temperature gauge spiked. That "cheap" part turned into a tow bill, a coolant flush, and a very unhappy operations manager.

My rule now: if a part is under $20 and it is on the cooling system, the fuel system, or anything pressurized, I order two. One goes on the vehicle, one goes in the shop cabinet. The carrying cost is trivial compared to the downtime cost.

Step 4: Know the replacement interval before you order the part

This one sounds obvious, but I got burned by it. A shop asked me to order a fuel filter. I ordered it. Three months later, they asked again. I assumed they were being careless—turns out our service schedule was wrong, and nobody had updated it since we bought the vans used.

If you're wondering how often to change fuel filter on your vehicles: check the owner's manual for the specific model, and then check whether your actual driving conditions (short trips, dusty environments, idling) match the "normal" or "severe" schedule. Most manufacturers put those intervals in two separate columns, and fleets almost always fall into the severe category without realizing it.

We now keep a simple spreadsheet with part numbers, intervals, and last-replaced mileage. It took about two hours to build and has prevented at least four "why are we ordering this again?" conversations.

Step 5: Confirm the supplier can actually invoice you properly

This is the step most people skip, and it's the one that cost me the most grief. In early 2023, I found a supplier with great prices on brake components. I placed a $1,800 order. The parts arrived fine. The invoice was handwritten. Finance rejected it. I spent three weeks chasing a proper invoice, and the vendor eventually sent something that looked like it had been typed on a 1990s word processor. Finance rejected that too.

I ended up paying out of the department budget and getting reimbursed two months later after a lot of emails. Now I ask two questions before any new vendor's first order: "Can you send a PDF invoice with your tax ID and our PO number on it?" and "Do you accept net-30 terms?" If the answer to either is shaky, I move on. Price savings don't matter if the paperwork doesn't clear.

Step 6: Check return policy and restocking fees in writing

Parts get ordered wrong. It happens. What matters is how much it costs you when it does. Some suppliers charge 15-25% restocking fees on electrical or special-order parts. Others won't take returns at all once the box is opened.

I now keep a one-line note in my vendor spreadsheet for each supplier: "Returns: 30 days, 15% fee, unopened only" or whatever the policy is. When I'm comparing two suppliers with similar pricing, the return policy is often the tiebreaker.

Step 7: Log the order—even if it's "just" a $12 cap

I resisted this for a long time because it felt like busywork. Then we had a situation where a radiator cap failed twice in six months. Because I had logged both orders (dates, part numbers, suppliers), I could show the pattern to the shop and we realized the issue was a warped filler neck, not bad caps. Without the log, we would have kept buying caps and wondering why they kept failing.

The log doesn't need to be fancy. Mine is a Google Sheet with six columns: date, vehicle, part number, description, supplier, and cost. That's it. It takes about 90 seconds per order to maintain, and it has paid for itself several times over in avoided repeat mistakes.

Common mistakes I still see (and occasionally make)

• Ordering by brand loyalty instead of fitment data. A brand you trust can still make a part that doesn't fit your specific vehicle. Check the numbers.
• Assuming "it looks the same" means it works. Two calipers can look identical from the outside and have different piston sizes or bracket offsets.
• Forgetting to update the schedule after a vehicle changes. When we swapped two vans between departments, the maintenance schedule didn't follow the vehicle. We missed an oil change by 4,000 miles because of it.
• Not asking the shop what they actually need. I once ordered a complete caliper assembly when the shop only needed the piston and seal kit. The return shipping cost more than the part.

Five minutes of verification beats five days of correction. I have the receipts to prove it—literally, in a folder labeled "mistakes."

If you take nothing else from this, take Step 1 and Step 5. Get the OEM number, and confirm the supplier can invoice you. Those two steps alone would have saved me about $1,200 and a significant amount of pride over the past three years.