Got a car you rarely drive? Then it probably needs special attention

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Our secondary vehicle only gets driven about 4,000 km a year. What should I do for maintenance? The user manual says it requires oil changes every six months/5,000 km, but which is it – every six months or do I wait until 5,000 km? And what about other maintenance? – Mike

If your owner's manual calls for an oil change every six months or every 5,000 km, always do whichever one comes first, experts say.

"It's always whichever one comes first, for everything. It's the short and easy answer to your question," said Calvin Feist, an instructor with the Northern Alberta Institute of Technology in Edmonton. "If you're not driving it much, it should be done whenever the time comes up."

Why? Because oil and other fluids break down over time. It might seem counterintuitive, but a car that spends most of its time in the driveway will probably need its oil changed more often than a car that is driven regularly.

Stephen Leroux, professor at Centennial College in Toronto, gives the example of a vehicle that requires an oil change every six months, or every 12,000 km, under normal driving conditions.

"You may be able to go even longer between oil changes if it uses a synthetic lubricant, under normal conditions," Leroux said. "But if you're only taking it out infrequently or on short trips, then the oil starts to deteriorate quicker, even if it's synthetic. You'll have shorter intervals between changes, like every six months or 8,000 km."

If the car doesn't spend enough time on the road to reach its optimal engine temperature, the engine might not get hot enough to burn off the water vapour that's produced during combustion.

That water vapour tends to mix with your oil and forms a milky sludge, and that could necessitate an even earlier oil change – say, every five or six months or every 6,000 km.

On top of that, if you're doing a lot of idling, you can get fuel carbons in the oil, which makes it acidic, and acid isn't good for your engine.

"It happens even if you're just driving to the store and back," Feist said.

One way to prevent moisture buildup and extend the time between oil changes is to take your vehicle out for regular jaunts on the highway. "It also helps the engine prevent carbon buildup," Leroux said.

Both Feist and Leroux say you should follow the schedule recommended in your owner's manual. Not following it can jeopardize your warranty.

Some auto makers will specify a schedule for low-mileage vehicles, just as they have a special schedule for vehicles that get really heavy mileage.

"They might refer to them as 'extreme service' or 'special operating conditions,'" Leroux said.

You also need to look at how often, and when, you drive the vehicle.

"My dad's vehicle, he just uses it in the summer to haul the trailer and it sits all winter," Feist says. "So in September or October he changes the oil."

While a car that gets driven throughout the year can probably follow the manufacturer's schedule, cars that sit through the winter should get their oil changed in the fall, so old oil isn't sitting in the engine.

"If it's parked all winter, it's also smart to put in a fuel stabilizer," Feist said. "And fill it up with fuel, so it's less prone to condensation."

On top of following the manual, Feist suggests talking to your mechanic about what additional regular maintenance your car might need.

"You should go to the repair shop you normally use and say 'Look, this is what we use it for, can you come up with a schedule?'"

And, generally, you should get in the habit of regularly checking fluid levels, lights and tire pressure, Leroux said. Monthly is a good idea, even if it's just a quick visual check.

"Vehicles that don't get used often tend to get neglected because owners feel that if it hasn't been used, what could possibly go wrong?" he said. "It's not the best mindset."

If you have any driving queries for Jason, send him a message at globedrive@globeandmail.com or contact him through Twitter: @JasonTchir