Why oil changes are important

Rarely has there been a better case in the real world to illustrate why changing oil precisely in accordance with the servicing schedule is imperative.

Here at carsales we’ve been contacted by Steve*, the concerned father of a 20-year-old woman, Olivia*. Just a month ago, and flush with cash and full of youthful enthusiasm, Olivia had bought herself a seven-year-old diesel SUV, one wearing a desirable prestige badge.

The car appeared to have a reasonable service history and the lady selling it was the original owner. While the odometer showed over 147,000km travelled from new, the vehicle was sound. Olivia happily handed over her $15,000 and drove away.

Just 16 days later, the engine failed catastrophically. The vehicle was transported to the nearest dealer and the service adviser there reported the unfortunate news. Tearing the engine down revealed that the timing chain had snapped, allowing the valves to come in contact with the pistons before the whole whirring, rotating panoply came to an abrupt halt.

Worse still, the cost of repairing the engine was calculated to be in the vicinity of $35,000. To put that in context – $20,000 more than Olivia paid for the car.

As it turned out, the dealer ascertained the car had been the subject of a less than perfect servicing regime. Critically, oil changes had frequently been delayed.

It goes without saying, as the car had been purchased privately, no warranty was in effect.

In good faith, the dealer negotiated with the manufacturer to supply the parts at cost and was also willing to assist on labour costs. But while this collectively reduced the cost by $10,000, Olivia was still looking down the barrel of a repair bill totalling over $24,000 – still around $10,000 more than the car was worth as a going concerning.

Oil lubricates parts high in the engine, such as camshafts and valve gear, plus the timing chain, as in this case; it also lubricates the big and small-end bearings and lower internals, such as pistons, connecting rods and crankshafts,

Oil that is breaking down after too long in the engine loses its ability to reach the engine’s extremities on cold starting and at the same time also loses its ability to form a protective film between hard-working parts.

Engine wear is increased in this situation, and piston rings can start letting oil into the combustion chamber, where it can burn as blue smoke and discharge from the exhaust.

A smoky engine will likely be reported to authorities, costing you money to fix, and ultimately part seizures can bring the engine to a complete halt, leaving you stranded and facing a big repair bill.

When carsales examined the case, a spokesperson for the manufacturer stated: “Our investigation shows the vehicle’s oil services were routinely late with a cumulative total of more than 18,000km past due”, thus, the company would not “accept liability for a vehicle not purchased through an authorised... dealer with poor oil service history”.

The vehicle’s electronically-recorded service history revealed:
• 4500km overdue for oil servicing in May 2019
• 5000km overdue for oil servicing in July 2018
• 6000km overdue for oil servicing in August 2017
• 220km overdue for oil servicing in August 2016
• 2800km overdue for oil servicing in November 2015

With many modern engines delivering condition based service messages, oil changes and the like are not strictly linked to set mileages.

Thinking you can continue to drive until a round number, 100,000km for instance, and delay the service is at best false economy. Indeed, with highly stressed and turbocharged small capacity petrol and diesel engines this can be a recipe for disaster. This appears to be the case in our engine failure example.

Right about now, readers are probably lining up to cast blame. But there are no real villains in this situation.

Without very careful scrutiny of the car’s logbook, Olivia can be forgiven for letting this one slip past her, but a pre-purchase inspection from RedBook Inspect or a state motoring association might have brought to light the car’s spotty service history.

Certainly the sludge in the crankcase and poor oil condition would have been apparent to a professional mechanic carrying out the inspection.

And to clarify, while the brand in question did have a reputation for similar failures in earlier engines, the engine in Olivia’s car was built two years after the last known examples of this syndrome. It appears to be very much a case of neglect on the part of the first owner.

And on that point, yes, the original owner of the car was negligent, but who hasn’t let a car’s major service go begging while waiting for a convenient time?

The important point here is not finding someone to blame, it’s about ensuring that something like this doesn’t happen to you. The message is simple: Change the dammed oil when it’s due.

* Not their real names

Picture shows the head of a Ford Falcon six-cylinder engine, with the timing chain disconnected from the camshafts and draped over the head in the lower right corner. It is not the engine that was the subject of this article. Courtesy of Liftarn/Wikimedia Commons.