When shopping for a pre-owned vehicle, one key thing you must check for is car maintenance. If the previous owner failed to maintain the vehicle properly, this can knock years off its useful life. 

You can start weeding out poorly maintained vehicles by looking for these tell-tale signs of poor car maintenance. While none of these issues should outright prevent you from purchasing the pre-owned car you love, they should push you to more thoroughly inspect the vehicle or take it to a repair shop for a third-party inspection. 

Here are the tell-tale signs of poor car maintenance to keep an eye out for. 

Missing Maintenance Records

Missing maintenance records are the first sign something is not quite right and needs extra attention from you. 

Meticulous car owners will have most -- if not all --their maintenance records neatly filed away and registered in their owner's manual. Some may even keep a separate spreadsheet of all the services and load the receipts onto a cloud service for easy access. 

Unfortunately, most car owners are somewhere in the middle of no record at all and neatly filed records. Many of us have half or a little more or less of our maintenance records, though we generally complete our maintenance on time. 

So, if there are some records, but others are missing, this isn't a reason to condemn a car. It's simply a reason to do more digging and deeper inspections. If there are no maintenance records at all, it's worth being a little more alarmed, but the same basic principle applies. 

Mismatched Tires or Uneven Tire Wear

When you replace tires, you should usually replace them in at least pairs -- preferably four at a time. The only exception is if the rest of the tires' tread are within 17 mm of the new tire. This ensures the tires will wear evenly and the vehicle will not pull to one side. 

Also, if you see severely uneven tire wear, this is a sign the previous owner had issues keeping up with the vehicle's maintenance — even something simple, like tire rotation, wheel alignment, and tire pressure. 

Some uneven tire wear to look out for includes outer or edge wear, outer and inner edge wear, centre wear, angled wear, and choppiness. These are all indications the owner ignored alignment, tire pressure, and rotation issues -- all among the simplest maintenance procedures. 

This can indicate that other simple but important maintenance went unperformed, such as oil changes, transmission services, and coolant exchanges.

Engine Oil Burned Onto the Dipstick

You’re supposed to check your oil every few weeks, so you should routinely remove the dipstick, wipe the old oil off, and reinsert it to get a proper engine oil level. Wiping off the old oil will help minimize the amount of oil that gets burned onto the dipstick due to the heat inside the engine. 

If the dipstick is so heavily covered in burned-on oil, the owner likely rarely checked the oil level. This is a warning sign the owner left other critical maintenance issues unresolved. 

Thick, Sludge-Filled Engine Oil

Heat and chemical contamination cause oil to turn into a thick sludge that can block it from flowing properly. This is why we change it at the manufacturer's recommended intervals. 

If you pull the dipstick and find the engine is thick and clumpy, this is excess sludge buildup from not changing the oil regularly. If the owner couldn't manage timely oil changes, there's a good chance other maintenance procedures, like replacing the spark plugs or changing the brake fluid, went without timely completion. 

Dark and Sticky Transmission Fluid

Automatic transmission fluid is often a forgotten maintenance item for so many vehicles. Today, most manufacturers recommend a transmission flush or a fluid and filter replacement at 60,000- to 100,000-mile intervals.

Because of the long intervals, this is an easy service to forget about, but it's still extremely important because this fluid is responsible for cleaning and lubricating the transmission, and creating the hydraulic pressure the transmission needs to shift gears.

If an owner skips this maintenance procedure, you'll find the transmission fluid may be dark (not bright red, as intended) and sticky. This can also be a sign that the lack of maintenance has caused damage inside the transmission, meaning a rebuild, which can cost $1,500 or more. 

Original Equipment Manufacturer (OEM) Oil Filter

Some people may take their vehicle to a car dealership for oil changes or request only the OEM oil filter when getting the oil changed elsewhere. But this is the minority. If you see an OEM oil filter -- one with the automaker's name on it -- on the vehicle, there's a good chance it hasn't been changed since leaving the dealership. 

Don't take this as clear-cut evidence of lacking maintenance, as this owner may be one of the minority of car owners who get even the simplest procedures done at the dealership. However, it is a reason to tighten your senses when looking for other signs of lacking maintenance. 

Check Engine Light Is On

A check engine light generally has nothing to do with maintenance, but it's a clear sign of some negligence. A check engine light is often something simple, like a sensor or even a loose fuel cap, so letting this light linger undiagnosed and unrepaired is a good reason to tighten your senses for signs of lacking maintenance the car needs.  

Severe Buildup on the Car Battery Terminals

Over time, hydrogen gas is released from your sulfuric acid in the battery. This causes a corrosive environment in the area, causing that white buildup you sometimes see on your battery terminals. 

Pour a little cola on the terminals or douse them with a chemical battery cleaner, and you're good to go in just minutes. Left untreated, this corrosion can impact the flow of power to and from the battery, potentially placing stress on the car's alternator. 

If you see a mountain of white corrosion on the battery terminals, this is a sign the owner rarely looked under the hood or cared little about maintenance. Make sure to go over the vehicle with a fine-toothed comb to ensure no other maintenance was left incomplete. 

Discoloured and Thick Coolant

There are many different types of coolants with all different colours. Yellow, green, and orange are the most common, but there is also blue, pink, and others. Find out the correct colour coolant this vehicle uses and compare it to what's in the radiator reservoir. 

If it has a hint of a rust colour or looks otherwise discoloured and thick -- coolant should have almost the same consistency as water -- this is an obvious sign the owner has ignored the coolant maintenance schedule.

Screeching or Grinding Brake Pads 

When it's time for new brake pads, they will often make a mild squealing sound as a reminder. This is nothing harmful. But once they get too low, the metal backing plates on the brake pads can touch the rotor -- the metal disc the pads grip to stop the vehicle -- and make a horrific grinding or screeching noise.

This is a tell-tale sign of poor car maintenance on the braking system. The owner went weeks or even months driving the vehicle with a squeal and didn't take the vehicle to a repair shop for a check-up. What other strange noises has this owner ignored? 

A Pre-Owned Vehicle From Clutch Will Ease All Your Worries

Don't want to stress about a vehicle's maintenance history or any other issues stemming from poor maintenance? Clutch, Canada's first 100% online pre-owned vehicle retailer has you covered. All our vehicles endure a 210-point inspection and reconditioning process to ensure there are no issues. 

We also back all our vehicles sold online with a 90-day or 6,0000-km warranty in case something does come up. 

Check out our inventory of quality pre-owned vehicles, find the one that suits you, and buy it all online. We'll deliver it to you and give you a no-risk 10-day or 750-km test-own period. If you don't love your Clutch vehicle within this period, we'll take the vehicle back and issue a refund or exchange it for another vehicle.