The most common fault on a used car is not the engine or the gearbox. It is worn suspension, found at moderate level or worse on 30 of every 100 cars in the Instant Auto Reach Inspection Index.
Here are the seven fault areas our inspectors find most, counted from 100 reports rated on the Instant Auto Reach Severity Scale.
| Rank | Fault area | Cars out of 100 |
|---|---|---|
| 1 | Suspension bushes, shocks and links | 30 |
| 2 | Engine oil leaks or residue | 26 |
| 3 | Cooling system | 21 |
| 4 | Driveline | 19 |
| 5 | Brakes | 18 |
| 6 | Fault codes or warning lights | 17 |
| 7 | Tyres | 15 |
1. Worn suspension bushes, shocks and links
Front lower control arm bushes are the single item we write up most. They crack and perish with age, and a short test drive will not show it. We found them cracked on a 2015 Toyota FJ Cruiser at 106,316 km, a 2018 Toyota Vitz Hybrid and even a 2024 Tesla Model Y. Read more in control arm bushes, our top finding.
2. Engine oil leaks or residue
These range from light seepage at a rocker cover to a suspected rear main seal, which means separating the gearbox from the engine to fix. A freshly washed engine bay is a flag in itself. We explain how we tell them apart in oil leaks on used cars.
3. Cooling system faults
Low coolant with no visible leak was the most common pattern. In the worst cases we found oil in the coolant or coolant residue under the oil cap, both possible signs of a head gasket problem. See low coolant explained.
4. Driveline wear
Leaking CV boots, cracked driveshaft couplings and, on 4WDs, differential locks that would not engage. If you are buying a ute, our ute and 4WD inspection tests low range and the diff lock, not just the road manners.
5. Brakes
Mostly worn pads and wavy or lipped rotors. These are cheap on a small hatch and expensive on an AMG. They also decide whether a car passes a roadworthy certificate.
6. Fault codes and warning lights
A scan tool sees what a test drive cannot. We clear stored codes, road test, then scan again to see what comes back. The method is in stored vs current fault codes.
7. Tyres
Worn tyres are easy money in a negotiation. Uneven shoulder wear also points to alignment or suspension problems, which loops back to fault number one.
What is not on the list
Previous body repair appeared on 9 in 100 cars and rust on 6 in 100. Less common, but far more serious when found. One car in the Index had been written off twice.
How to use this list
Most of these seven are negotiation items, not deal breakers. One buyer told us in a Google review that our inspector found an oil leak, which really helped when negotiating the price. Our guide on how to negotiate after an inspection shows how to turn a report into a number.
The full dataset is in what 181 Melbourne inspections found. To get these checks on the car you are looking at, book a pre-purchase inspection.
Find the Faults Before You Pay for Them
Worn bushes, oil leaks and cooling problems do not show up in a test drive. They show up a few months after you have paid. Every one of the seven faults above is something our inspectors check on every car, with photos and a severity rating you can take straight to the seller.
Most of these faults are not reasons to walk. They are reasons to pay less. Book an inspection and walk into the negotiation with the evidence in your hand.
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