SINGAPORE - Certificate of entitlement (COE) prices for cars reached dizzying heights last month when premiums spiked across all three categories.

Big-car buyers were left gobsmacked as the Open COE crossed the $70,000 mark and Category B trailed by a mere $1,700.

While Category A (cars up to 1,600cc) prices dipped this week, premiums for big cars (above 1,600cc) continued to surge and are now at their highest levels since June 2015.

Adding to their woes, some buyers are also facing a longer wait for their new cars due to shipment delays. A prolonged computer chip shortage has forced carmakers to cut production, although most brands here are unaffected because of existing inventory and the quota system.

Small wonder then that the used car market is booming. Buyers in the secondary market do not need to cough up so much cash upfront and they usually get their cars instantly.

There are several pitfalls to avoid when it comes to buying a used car. Still, if you do your homework, you can snag a good deal.

Read car reviews and join car forums to find out the experiences of other consumers. Find a trusted mechanic who specialises in the make and model of the car that you are eyeing. Most reputable car dealers allow you to put the car through a thorough inspection after a deposit has been placed.

During viewing, it is easy to be enamoured with a gleaming ride, especially if the dealer has polished or even resprayed the vehicle. Do not be too fixated on the exterior aesthetics. Rather, scrutinise the interior as well as the trip meter.

The average car clocks about 16,500km a year. Alarm bells should ring if the seats and steering wheel look worn in relation to the car's mileage. This could mean the odometer has been tampered with.

Open the bonnet and check the engine oil and coolant levels. Look out for black oil stains in the engine bay as this may be a sign of an oil leak. Brownish coloured coolant possibly indicates a rusty radiator as most coolants are pink, blue or green in colour.

A shiny new radiator could also mean the previous owner got into an accident recently. Most head-on collisions damage the radiator as this component is usually placed right behind the front grille.

While most used car dealers do not allow test drives, you can start the engine and listen to the idling sounds. Shift the transmission to neutral and step on the accelerator to hear the revs as well. A well-serviced engine sounds smooth and is void of any strange metallic noises.

However, even with all the due diligence, you can still meet a rogue car seller.

I had a brush with one when I was viewing a BMW 316i two months ago. The car was advertised by a direct seller and indicated 87,000km on its odometer. It satisfied all my visual checks and I had one last test to perform before placing the deposit.

I used a Carly OBD reader, a vehicle diagnostic tool, to check the mileage. To my horror, the scanner indicated an actual mileage of 171,000km.

Citing mileage tampering, I called off the purchase. To my surprise, there was not a hint of protest from the seller, which all but confirmed my suspicion.

Thankfully, I soon found a similar unit with a genuine mileage of 50,000km at a used car dealer. It passed all my checks, including the mileage tampering check with the Carly OBD reader.

After placing the deposit, I sent the car for another round of inspection with my mechanic before sealing the deal.

A used car in good condition does not mean there is no need for any repairs. I did a full servicing, replaced the charge and boost pipes, engine mounts and tyres. After all, it is a seven-year-old car, and some wear and tear is to be expected.

Keep all the servicing records and receipts as they go some way in helping you sell your car when the time comes. They certainly helped me sell my 12-year-old Suzuki Swift Sport in five days after I put it up for sale.