When should I change my car's oil?

The oil circulating around an engine keeps the moving parts within the engine lubricated. Without the lubricant, the moving parts will wear faster where they make contact with other moving parts, and before long the owner of the car will be facing a very expensive repair bill.

So, when is the magic moment that the oil change in a vehicle should take place? If you  leave it too long grit or particles from the engine parts making contact with each other will accrue in the oil. The more these particles affect the viscosity of the engine oil, the less effective the oil is. A regular oil change in line with the recommendation of the car manufacturer will save the vehicle owner many thousands of dollars down the track.

The log book for your car (AKA the owner's manual) will tell you how often the oil in the engine should be changed. And when in doubt, feel free to discuss with a service adviser whether to replace the engine oil more often, if you feel there are reasons why the interval may not apply in your case.

The Hyundai Santa Fe Highlander long-term test vehicle that has been undergoing evaluation by carsales comes with an owner's manual that indicates the engine oil (and the oil filter) should be replaced at least once every 12 months or 15,000km, whichever occurs first.

But Hyundai also leaves the way open for an oil change and new oil filter at half the usual interval in certain circumstances: that would be every 7500km or six months, whichever occurs first.

These circumstances are as follows:

A. Repeatedly driving the car short distances of less than 8km in normal temperatures or less than 16km in freezing temperatures.
B. Extensive engine idling or low speed driving for long distances.
C. Driving the car on rough, dusty, muddy, unpaved, gravelled or salt spread roads.
D. Driving the car in areas using salt or other corrosive materials or in very cold weather.
E. Driving the car in heavy dust conditions.
F. Driving the car in heavy traffic areas.
G. Driving uphill, downhill, or on mountain roads repeatedly.
H. Towing a trailer, or using a camper or roof rack.
I. Driving a patrol car, taxi, commercial vehicle or vehicle towing.
J. Driving the car over 170km/h.
K. Frequently driving in stop-and-go conditions.

These stipulations have been formulated for global markets, not just Australia, and some can be discounted. It's very unlikely that Australian Santa Fe owners will be regularly driving at over 170km/h, for instance. Nor do we spend a lot of time driving in sub-zero temperatures, unless we live and work in the mountains. And we don't spread salt on the roads here during the winter months.

But most of the Hyundai points are useful guides for not just Santa Fe owners, but owners of other vehicles too. We would also add that if your car spends a lot of time on a racetrack or in some other extreme driving situation not covered by Hyundai's list, that also warrants an oil change for the engine sooner rather than later.

Bear in mind too that if your car is older, but subject to the same extreme driving conditions mentioned, consider an oil change as frequently as every 5000km. Choose a better class of oil with the right viscosity for your needs if you're changing the oil and filter yourself. A lighter oil is better if your car spends a lot of time in a cold climate, as an example. In the event that the engine of your car is built to fine tolerances, the manufacturer will usually recommend a lighter oil that will reach the extremities of the engine from the sump as quickly as possible after starting.

The owner of an exotic car with a sophisticated engine is well advised to consider a synthetic oil for the oil change. A synthetic oil will hold up better under hotter operating temperatures, when racing for instance. Otherwise, the car owner can opt for conventional oil, since it is cheaper and will do the same job in normal conditions. For much the same reason, be prepared to pay more an oil filter developed for high-performance engines or heavy-duty applications if that's appropriate.

If you feel confident you can carry out an oil change without taking the car to professionals for a full-service oil change, you will need an appropriate spanner and/or socket for loosening and then replacing the drain plug. Additionally, an affordable tool to loosen the oil filter can be purchased from an aftermarket parts and tool retailer. An old trick to remove the oil filter is hammering a screwdriver through the thin metal shell of the filter and use the screwdriver to unscrew the filter from the engine block. Don't try this if you haven't seen it done before, but equally, don't worry about damaging the filter during its removal. It's a throw-away job after it has been removed.

Also, don't forget to slip a drain pan under the sump of the vehicle, which will have to be jacked up first. Otherwise, you'll have engine oil spilling all over the clean concrete floor of your garage. And of course, exercise the appropriate care by using jack stands or wheel ramps to keep the vehicle supported securely while raised.

Finally, do change the oil filter at the same time as the oil. In the past it was common for the filter to be changed every second oil change, but for the sake of a few dollars, a new filter will keep the oil free of damaging particles for longer.