Buying a used car checklist: what to check before you pay

What should a used car checklist include?

A used car inspection checklist should follow the order of the visit, because each stage decides whether the next one is worth your time. A paperwork problem ends the visit before you open the bonnet. The table below lists the six stages, what to look at in each, and why that stage matters on its own.

What should you bring to inspect a used car?

Bring a torch, a cloth for the dipsticks, a tread gauge or, for the American test below, a US quarter, and an OBD2 adapter or scanner. Go in daylight, because paint repairs and panel colour differences are hard to see under street lights or in rain.

Consumer Reports asks the seller not to drive the car for at least an hour before the inspection. Asking for a cold engine also lets you hear a cold start, when many engines show their problems, so an engine already warm when you arrive is a reason to ask why.

Paperwork, V5C and VIN: what to check before you touch the car

Start with the VIN, the 17-character vehicle identification number. It should match on the dashboard plate, the driver's door jamb and the V5C log book. Then ask for service records, and compare the mileage on oil-change stickers and invoices with the odometer. In Britain, also check the MOT history online, which records the mileage at each test.

A history report comes next, and it is a filter rather than a verdict. In Britain, a paid history check is the usual route, alongside the MOT history above. In the US, an NMVTIS report covers title, odometer and certain damage history for up to $4, and the National Insurance Crime Bureau offers a free VIN lookup that includes flood damage. Our guide to free vehicle history reports compares the options.

A report does not replace an inspection. The US FTC notes that a history report may show accidents and flood damage, but typically will not list mechanical problems.

As a US reference, at a US dealer read the Buyers Guide, which the FTC requires in every used car offered for sale. It says whether the car is sold with a warranty or as is, and as is means the dealer will not pay for any problems or repairs. Federal law does not require dealers to give you three days to cancel, so the check has to happen before you sign. These are US rules and your rights as a buyer differ by country, so check what applies where you are buying.

Body, tyres and flood signs: what to look for outside

Walk around the car and look along each side from low down, where ripples and colour differences show. Then check these points, each of which can lead to a repair bill or a lie about the car's past.

• Panel gaps. The gaps around the bonnet, boot and doors should be even. An uneven gap suggests a panel that was removed or a past collision repair.
• Paint and rust. Look for overspray on rubber trim and for a colour that changes between panels. Check wheel arches and the bottoms of doors for rust.
• Tyre tread. Consumer Reports gives the US legal minimum as 1/16 inch (about 1.6 mm). Its test is American: push a US quarter into the tread with Washington's head down, and if you can see the top of his head the tyre should be replaced.
• Tyres against mileage. A car under about 20,000 miles should probably still wear its original tyres. New tyres on a car that low on the clock deserve a question.
• Flood signs. The Missouri Attorney General lists a musty or over-perfumed smell, water stains or mud under carpets and mats, and rust in odd places such as upper door hinges, boot latches and console screws.

Under the bonnet: what the fluids tell you

Open the bonnet and read each fluid, wiping the dipstick with the cloth before you judge the oil. Do the oil and coolant with the engine cold. Consumer Reports, in a checklist updated in March 2026, says to check transmission fluid with the engine warmed up and running, so read that one after the test drive. Also look for leaks, cracked belts and soft hoses.

Interior and warning lights: what to check inside

Turn the key to on without starting the engine. The warning lamps should light up, then go out once the engine runs. A check engine lamp that never lights deserves a question, and one that stays on is a fault to ask about. Auto Care Plus lists both checks in its pre-purchase checklist.

Then compare wear with the odometer. In Britain, also check the MOT history online, which records the mileage at each test. Kelley Blue Book, citing NHTSA in 2018, reports a US estimate of more than 450,000 vehicles sold each year with false odometer readings, and says pedals, brakes and wipers should match the mileage shown.

Consumer Reports suggests asking why when a car averages more than 20,000 miles or fewer than 5,000 miles a year. Our guide on how much mileage is too much covers what to expect at each age. Finish by testing every window, lock, seat, the air conditioning and the heater.

What to check on a used car test drive

Drive the car from cold, on a route with a rough road, a stop and a stretch of motorway. Keep the radio off. Auto Care Plus lists test speeds of 30 mph, 45 mph and 60 mph, which covers the gears and the speeds where vibration appears.

• Cold start. The engine should start promptly and settle to a steady idle, with no blue or white smoke from the exhaust and no warning lamps left on.
• Steering. The car should hold a straight line on a flat road, without pulling, and the wheel should not shake at motorway speed.
• Brakes. Brake firmly from a moderate speed where it is safe. The car should stop straight, with no grinding, pulsing pedal or pull to one side.
• Shifting. An automatic should change gears smoothly, with no slipping or delay. A manual clutch should bite cleanly, not at the very top of the pedal.
• After the drive. Park, leave the engine running and look under the car for fresh drips. Check that the temperature gauge stayed in its normal range.

How to scan a used car with an OBD2 reader before buying

An OBD2 scan reads the car's own diagnostics through the port under the dashboard, and it needs the seller's permission and about as long as it takes to look at the tyres. The California Air Resources Board says OBD II is required in the US on petrol cars and trucks from model year 1996 and on diesels from 1997. Other markets have their own dates, so check the year of the car you are viewing. If you have never used one, read how to use an OBD2 scanner first.

The check that matters most is a recent clear. Clearing a code turns the check engine light off, but it also resets the readiness monitors, the self-tests the car runs while driving. The New York DMV lists clearing codes among the causes of a car being not ready, along with a disconnected or replaced battery.

Not ready is a question, not a verdict. The battery may simply be new, and the California Air Resources Board says about a week of normal driving usually completes the indicators. California's Smog Check has let the evaporative monitor stay unset on petrol cars from 2000 on, and rules effective October 2025 move toward requiring every monitor, so one incomplete monitor alone means little. Several incomplete on a car with no recent battery work means ask why.

Permanent codes are the second check, and clearing cannot remove them. The California Bureau of Automotive Repair says they cannot be cleared by a scan tool or by disconnecting the battery, on model-year 2010 and newer vehicles that support them. They clear themselves only after the monitor runs again and finds no problem.

WrenchTime is an iPhone app that logs a vehicle and reads it. With a Bluetooth Low Energy ELM327 adapter or the OBDLink MX+, its Trouble Codes tool, part of WrenchTime Pro, reads stored, pending and permanent codes from every module that answers the standard request, with the check engine status, readiness monitors and freeze frame. The OBD-II code reader for iPhone guide shows how, and any other scanner that reads these items does the same job.

• Never clear anything. A scan only reads. Clearing changes someone else's car and resets the very evidence you came to see.
• Compare the VIN. Many cars report their VIN over OBD2. It should match the dashboard plate, and a mismatch deserves a question.
• Know the limits. A clean scan says nothing about the body, the suspension or wear. Standard OBD2 covers emissions diagnostics and does not read manufacturer-specific codes.

How much does a pre-purchase inspection cost?

A pre-purchase inspection is a mechanic's check of a car you do not own yet, and in the US it usually costs $100 to $200. Consumer Reports puts a thorough one at around $100 to $150, and Cars.com quoted a RepairPal estimate of $132 to $200 in 2024. These are US figures, and prices in Britain differ. Rarer cars can cost more, so ask the price first.

The FTC calls an independent inspection always a good idea and tells buyers to ask for a written report with a cost estimate for all necessary repairs. That report is also your negotiating tool, because a seller finds it hard to argue with an estimate from a third party.

When should you walk away from a used car?

Walk away when a problem is about honesty rather than wear. A worn clutch has a price, and a seller hiding a fault does not. Any one of these signs is enough to leave, however good the car looks.

• The seller refuses an inspection. No honest seller loses anything by letting your mechanic look. The same goes for a refused read-only scan.
• The paperwork does not agree. A VIN that differs between the car and the V5C, or a V5C in someone else's name with no explanation.
• The odometer does not fit. Service records with higher mileage than the dashboard, or wear far beyond what the mileage suggests.
• Flood signs. Mud under carpets, a musty smell, or rust in places water should never reach.
• Fluids that point to the engine. Foamy gray oil or milky coolant, unless the price already pays for an engine repair.

Used car inspection checklist for a hybrid or electric car

A hybrid or electric car goes through the same paperwork, body, interior and test drive stages, and adds one question: the state of the high-voltage battery. An electric car has no oil to read, so the engine bay stage shrinks to coolant, brake fluid and the 12-volt battery. Read how long hybrid batteries last or how long EV batteries last before you visit, and ask the seller for any battery health report.

Keep the car's history from the first day

Scan the car again the day you buy it, so you have a dated baseline. WrenchTime keeps each Trouble Codes scan with its date and odometer reading, and logs fuel, service and running costs in the same place, which also gives you the maintenance records you wished the last owner had kept. The free version covers 1 vehicle with 2 maintenance entries per month, and Trouble Codes are part of WrenchTime Pro.