Should I sell my car before 100,000km?

For decades, 100,000 was the magic number in the used-car market. Tick over six figures on the odometer and suddenly buyers got twitchy, dealers sharpened their pencils, and resale values often started heading south faster than a backpacker in winter.

But is 100,000km really the beginning of the end for a modern car, or is it just an outdated hangover from a time when engines, transmissions and rust protection weren't nearly as sophisticated as they are today?

The answer, increasingly, is that mileage is only one small piece of a much bigger puzzle.

There's no getting around it: lower kilometres generally mean more buyers and more money when you go to sell your car.

Punch two otherwise identical vehicles into the carsales classifieds and the one showing 70,000km will almost always attract more interest than the example showing 170,000km.

Part of that is psychology.

Many Australians still view 100,000km as a milestone where expensive repairs start lurking around the corner. And to be fair, they're not entirely wrong.

For petrol and diesel vehicles, major maintenance items often begin appearing around this point. Timing belts, water pumps, suspension components, coolant hoses, spark plugs, clutches and transmission servicing can all start demanding attention.

The trick is remembering that 100,000km isn't a death sentence. It's simply a stage in the ownership journey.

The fact many manufacturers now offer warranties stretching well beyond 100,000km further reinforces the point. Some brands, like Mitsubishi, cover their vehicles for up to 200,000km, while others have adopted unlimited-kilometre warranties altogether.

They aren't doing that because they expect their products to fall apart the moment the odometer ticks into six figures.

That's not to say warranties and reliability are the same thing. But it does highlight how far vehicle engineering, manufacturing and durability have come compared to the era when 100,000km was widely viewed as the beginning of the end.

It should also be noted that two cars with identical odometer readings may have vastly different futures.

Indeed, not all kilometres are created equal.

A car that has travelled 150,000km between Melbourne and Sydney on the Hume Highway may actually have experienced less wear than a vehicle showing 80,000km that's spent its life crawling through stop-start urban traffic.

How the kilometres were accumulated makes a difference, so does where they happened. The thing is, it’s often hard to ascertain such details, especially if the used car you’re buying has had multiple owners. 

There are services out there that can provide more clarity around mechanical wear and tear, such as a pre-purchase inspection from the likes of Redbook Inspect.

Other factors at play when looking to buy or sell a used car around 100,000km mark include environmental conditions, which can be particularly punishing in their own way, especially in Australia.

Intense UV exposure can fade paint, damage plastics and harden rubber seals. Coastal vehicles can suffer accelerated corrosion thanks to salty air.

Overseas, buyers face different challenges. North American and European vehicles often encounter road salt during winter (used to reduce snow and ice accumulation), which can attack underbody components and lead to corrosion issues years later.

And then there are the really niche concerns. In New Zealand, the notorious Kea, a curious alpine parrot, has become famous for attacking parked cars by tearing at window seals, wiper blades and exterior trim.

The point is simple: understanding where a vehicle has lived can be just as important as understanding how many kilometres it has travelled.

A stamped logbook remains one of the most valuable assets a used car can have. But savvy buyers increasingly look beyond the stamps.

Some buyers specifically seek vehicles serviced exclusively through a manufacturer's dealer network for precisely this reason. And the argument is straightforward: a Toyota serviced at an authorised Toyota service centre should, in theory, have received the correct fluids, procedures, software updates and genuine components.

Others will argue a quality independent workshop can perform identical work, often at a lower cost. Both camps have valid points.

The key takeaway is that a service history should be viewed as a starting point for investigation rather than a guarantee of condition.

Electric vehicles (EVs) are starting to reach an age where Australians can assess how they actually hold up over time rather than relying purely on manufacturer claims.

Early Nissan LEAFs, once viewed by some as disposable technology, are still appearing on the used market and continuing to serve owners well.

At the time of writing there were 66 electric Nissan LEAF city cars for sale on carsales, including a first-gen model from 2011 – and it’s still going.

There were also three LEAF hatchback EVs with more than 160,000km on the clock. One in West Australia had 223,000km. Not a bad effort.

That doesn't mean battery degradation isn't real. It absolutely is.

Like an engine slowly losing compression over hundreds of thousands of kilometres, EV batteries naturally lose capacity as they age.

The difference is that buyers now have increasingly sophisticated ways of measuring it. Battery health testing is quickly becoming the electric equivalent of a mechanical inspection.

According to carsales research, battery condition remains the biggest concern among prospective EV buyers, with 59 per cent identifying it as their primary hesitation when considering a used electric vehicle.

That's why services such as RedBook Inspect's EV battery health assessment are gaining traction. The tests measure a battery's State of Health (SoH) and provide independent data on remaining capacity and performance.

Mobile EV battery health testing is now available and these tests are designed to provide transparency around battery condition and improve confidence in Australia's growing used EV market.

The broader trend appears encouraging.

Previous battery health reporting referenced by carsales found average battery health exceeded 90 per cent, even among EVs that had travelled beyond 120,000km.

A research report from last year also noted some four-year-old EVs averaged at least 93 per cent battery health.

The old idea that cars should be treated like smartphones and replaced the moment they hit an arbitrary number is looking increasingly outdated.

For internal combustion vehicles, modern engineering, better lubricants and improved manufacturing mean many cars can reliably travel well beyond 200,000km when properly maintained. Anyone remember that one-million kilometre Toyota LandCruiser for sale recently?

For EVs, we're entering an era where battery health can be measured independently rather than guessed, removing much of the uncertainty that once surrounded older electric cars.

That doesn't mean every 150,000km bargain is a smart buy.

But for many modern cars, 100,000km is no longer the warning sign it once was. Condition, maintenance history and, increasingly, battery health tell buyers far more about a vehicle's future than the odometer alone.

Perhaps the better question isn't whether a car has travelled 100,000km. It's how it spent those 100,000km.

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