You found a used car on Facebook Marketplace. The price is right, the photos look good, and the seller seems reasonable. You're tempted to just go look at it, take it for a drive, and pull the trigger.
Don't.
Before you hand over a dollar, spend $100–$200 on a pre-purchase inspection (PPI). If you use a mobile mechanic to do it, even better — because they can meet you at the seller's location and inspect the car right there, on the spot, without you having to own the thing first.
What a Pre-Purchase Inspection Actually Covers
A proper PPI isn't a five-minute walk-around. A qualified mechanic will go through the car systematically:
- Fluid levels and condition — oil, coolant, transmission fluid, brake fluid. Dark, burned, or contaminated fluids tell a story.
- Undercarriage inspection — rust, frame damage, leaks, worn suspension components
- Brake condition — pad thickness, rotor wear, caliper function
- Tire wear patterns — uneven wear can signal alignment problems, suspension wear, or a car that's been driven hard
- Engine and transmission behavior — cold start, idle quality, shifting under load
- Lights, HVAC, electronics — the boring stuff that's expensive to fix
- OBD-II scan — checks for stored fault codes, including ones that were recently cleared to hide a problem before the sale
- Body and paint inspection — signs of prior accidents that weren't disclosed
A good mechanic will also flag anything that doesn't add up — mileage inconsistencies, mismatched paint, replaced panels, or a VIN that doesn't match the title.
Why Mobile Mechanics Are Ideal for This
Here's the problem with telling a private seller to bring their car to a shop: most won't. And if they do, you still don't know if they've taken it to a dealer first to get codes cleared or cosmetic issues addressed.
A mobile mechanic changes the dynamic entirely. They come to wherever the car is — the seller's driveway, a parking lot, a dealership. The seller doesn't have time to prepare. You get the car as it actually lives.
Mobile mechanics typically charge $100–$200 for a PPI depending on your area. Some do video walkthroughs so you have a record of exactly what was found and when.
What a PPI Can Save You
The math is straightforward. If a PPI costs $150 and reveals a failing transmission, head gasket issues, or a frame that's been welded back together after a serious collision — you've just saved yourself anywhere from $2,000 to $10,000+. Or you use the findings to negotiate the price down.
People skip PPIs because they feel awkward asking, or because they're excited and don't want to slow down the deal. That's exactly what sellers are counting on.
Red Flags a PPI Commonly Uncovers
- OBD codes recently cleared (common when a seller is hiding a check engine light)
- Frame or unibody damage not mentioned in the listing
- Evidence of flood damage — musty smell, water stains, corroded electrical connectors
- Mismatched paint or body panels from a prior accident
- Worn brakes or tires that need immediate replacement
- Leaking seals or gaskets that the seller "didn't know about"
The Bottom Line
If a seller refuses to allow a pre-purchase inspection, that tells you everything. Walk away.
A car that's in good shape can handle a mechanic looking at it. The ones that can't are exactly the ones you don't want to buy.
Ready to find a qualified mobile mechanic for a PPI? Visit /find-a-mechanic/ to locate vetted mechanics in your area.