How often should you change your engine oil?

Modern engines today are a technological marvel. Car manufacturers around the world have been designing engines to be environmentally friendly, very economical and incredibly powerful. The use of high-tech alloys and computer controlled mechanicals has enabled engine designers to build engines which 20 years ago would have been unheard of.

Today’s engines have amazing new components like variable camshaft control and variable valve openings, just to name a few. All these new systems and devices have increased the amount of internally moving parts inside the engine, particularly the cylinder head.

Strict environmental controls and emissions standards, and consumer demands for better fuel economy and performance have also forced designers to develop direct injection systems for both petrol and diesel engines.

These new injection systems now inject fuel directly inside the combustion chamber instead of inside the inlet manifold. The advancement in technology has enabled this super-efficient design to now become available in most new vehicles.

Technology Often Creates New Problems

Sometimes however, technology generates new problems. Take the inlet manifold, for instance. Once, there was a carburettor sitting on top of the engine. Air mixed with fuel was delivered above the throttle, which was awash in petrol, one of the world’s great solvents. So carbon could not build up because of the washing action of the swirling, fuel laden air.

Direct injection doesn’t have the fuel mixed with the air, so the natural cleaning action of the petrol can’t occur anymore. So yet again the introduction of new and better systems has by their very design caused an unintended problem.

As a result, it’s common now to find vehicles with dirty inlet manifolds and throttle bodies caused by carbon build up which can cause some components to stick and fail. In extreme cases, the blockages can cause the airflow entering the engine to become restricted. Such an obstruction can result in poor idle, engine stalling and a drop in performance and fuel economy. Customers often complain of a loss of power or poor fuel economy.

Another issue modern engines face is one which can be easily preventable. It’s the fact that many engines are creating huge amounts of internal sludge.

This sludge is caused by excessively long oil change intervals. Oil change intervals followed under car manufacture’s maintenance programs, as well as intervals indicated by the vehicle’s on-board oil change reminder system, are often too long.

Additionally, this is compounded by shorter drive times, as the condensation and acids in the oil do not get hot enough to burn off. Technically, oil sludge is the breakdown product of over-stressed oil in your engine.

What Causes Engine Sludge?

Oil that is stressed by contaminants and oxidation, or it has to work longer than it was really designed to, will break down and form a gel that sticks to your engine parts. As the gel or sludge sticks, there is less good oil to circulate and do its protective work.

Sludge contaminated engines are being damaged every minute they’re operating. Sludge can also block oil galleries and pipes, resulting in loss of oil pressure. This lack of oil pressure and flow can cause catastrophic component failures like worn timing chains and bearing failures.

Engines Use and Burn Oil

Sludge and carbon build up can also cause engines to use or rather burn oil, resulting in annoying and costly oil top ups as well as blowing smoke from the exhaust. The combination of carbon build up and sludge around the piston rings creates a situation where the oil control rings can’t scrape the oil off the bores during the piston’s downward stroke. Normally oil would flow from the rings and then through the small drain holes behind the rings. If the drain holes are blocked then the oil remains on the surface of the bore and consequently gets burnt during the engine power stroke.

Six Monthly Oil Changes

We recommend changing the oil in your vehicle every 10,000 km. Checking and changing the oil is essential to keep today’s engines working smoothly and efficiently.

You can check the oil level with the car parked on level ground. Open the bonnet and remove the dip stick and wipe with a clean cloth or paper towel then place it back in the dip stick tube. Pull it out again and see if the level is within the acceptable range marked on the dipstick. If you add oil yourself do not overfill. Overfilling can damage the engine.

Most auto manufacturers recommend oil changes once each year or 20,000km on petrol engines. Diesel engines and turbo charged petrol engines should be changed every 6 months or 10,000 km.

Changing the oil once a year (20,000 km) is OK for vehicles driven in ideal circumstances. However, normal driving for most people is actually severe service driving. This includes frequent short trips, (less than 15km especially in cold weather), stop and go city traffic, dusty conditions and sustained highway driving during hot weather. For this kind of driving it’s recommended to change the oil every six months or 10,000 km.

For maximum protection most auto shops recommend changing the engine oil every six months or 10,000 km regardless of the driving you do. Regular oil changes are cheap insurance against premature engine wear and will always save you money in the long run, particularly if you plan to keep the car for three or four years. It’s very uncommon to see engines that have been well maintained with regular oil changes develop any major rings, valves or bearing issues under 200,000 km.

What About The Oil Filter?

To reduce the cost of ownership and maintenance many car manufacturers say to replace the oil filter every other oil change. Most mechanics will tell you this is false economy.

Oil filters on most engines have been down sized to reduce cost, weight and space. The standard one litre sized filter once common on most engines has been replaced by a smaller half litre sized capacity filter. It’s not difficult to figure out the smaller filter has less filtering capacity.

These smaller filters however, are adequate for 5,000km oil change intervals, but will run out of capacity long before a second oil change at 10,000 or 20,000 km. Replacing the oil filter each time the oil is changed is highly recommended.

Filter Replacement

If you do your own oil changes make sure you get the right filter for your engine. Many filters look the same but have different internal valving. For example many overhead cam engines require an anti-drain back valve to prevent oil draining out of the filter when the engine is switched off. This allows oil pressure to reach critical engine parts more quickly when the engine is restarted. Filters mounted sideways on the engine usually require an anti-drain back valve.

Used motor oil needs to be disposed of correctly. The best way to dispose of used motor oil is through a licenced auto repairer or recycling facility. Don’t dump used motor oil on the ground, down a drain, into a storm sewer or place it in the rubbish. Most landfills will not accept used oil even if it’s in a sealed container because it will eventually leak out into the ground.

If you can’t find an environmentally acceptable way to dispose of your used oil and filters, maybe you shouldn’t be changing your engine oil at all. Service facilities like ours have recycling programs and licenses to dispose of used oils which are usually re-refined as other lubricants or burned as fuel.