Choosing the Right Engine Oil for Your Car

 

Picking the right engine oil isn’t just a box-ticking exercise at service time. The oil you use affects engine protection, fuel efficiency, and long-term reliability. With so many grades and types on the shelf, it’s easy to grab the wrong one. 
 

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Here’s how to choose oil that actually suits your car and how you drive it.

Understanding How Engine Oil Works

Engine oil does more than just lubricate moving parts. As it circulates through the engine, it forms a protective film that reduces friction between metal surfaces, helping to minimise wear. It also carries heat away from critical components, preventing hotspots that can damage the engine over time.

On top of that, engine oil traps dirt, soot, and other contaminants, keeping them suspended until they’re removed at the next oil change. It also helps prevent corrosion by coating internal surfaces and reducing moisture build-up. Using the wrong oil can disrupt all of this, leading to noisy starts, poor fuel economy, sludge formation, or accelerated engine wear. Choosing the right oil keeps everything working as it should.

Understanding Oil Viscosity Grades

Oil viscosity tells you how thick or thin your engine oil is and how it behaves in both cold starts and normal operating temperatures. Grades like 5W-30, 0W-20, and 10W-40 indicate how easily the oil flows when the engine is cold and how well it maintains protection once the engine is warm.

The first number (before the “W”)

This shows a cold-start performance. The lower the number, the faster the oil flows when the engine is cold, helping reduce wear on startup.

Examples: 0W flows faster than 5W or 10W.

The second number (after the dash)

This shows how thick the oil stays at normal operating temperature. Higher numbers mean thicker oil and can suit older or harder-working engines.

Quick examples

• 0W-20: Modern engines focused on fuel efficiency
• 5W-30: Common all-round oil for many cars and SUVs
• 10W-40: Often used in older or higher-kilometre engines

Using the wrong viscosity can affect oil pressure, startup protection, and long-term engine wear, which is why matching the correct grade matters.

Engine Oil Viscosity Comparison

Oil Grade	Cold Start Flow	Operating Temp Thickness	Typical Use
0W-20	Very fast	Thin	Newer engines focused on fuel efficiency and low emissions
5W-30	Fast	Medium	Most modern passenger cars and light SUVs
5W-40	Fast	Thicker	Turbocharged engines, mixed city and highway driving
10W-40	Moderate	Thicker	Older vehicles or higher-kilometre engines
15W-40	Slower	Thick	Diesels, 4WDs, towing, and heavy-duty use

Lower first numbers improve cold-start protection, while higher second numbers provide better protection under heat and load. Always prioritise the viscosity specified by your vehicle manufacturer.

Start With Your Manufacturer’s Specs

Always check your owner’s manual first. Manufacturers specify an oil viscosity grade and standard that suits the engine’s clearances and operating temperatures. Common viscosities you’ll see include:

• 5W-30 – Popular for modern passenger cars and light SUVs
• 0W-20 – Common in newer engines focused on efficiency
• 10W-40 – Often used in older vehicles or higher-kilometre engines

Ignoring these specs can affect oil pressure and protection, especially on cold starts.

Understanding Oil Types

Not all oils are created equal. Here’s a simple breakdown:

Mineral Oil

Mineral oil is best suited to older vehicles, classic engines, or simple mechanical setups that don’t run high temperatures or tight tolerances such as early Holden Commodores, older Ford Falcons, and classic Land Cruisers. It’s affordable and reliable, but it does need more frequent oil changes.

Examples include Penrite Premium Mineral PRO 20 20W-50, commonly used in older petrol engines, and Penrite Convoy Diesel HD 15W-40, which is well suited to older diesel vehicles and light commercial applications.Penrite Mineral Stops Oil Burning is also popular for high-kilometre engines showing signs of oil consumption.

Semi-Synthetic Oil

Semi-synthetic oil blends mineral and synthetic bases, offering better protection and stability without the higher cost of full synthetic. It’s a solid choice for daily drivers, mixed driving conditions, and engines that see regular use.

Penrite Everyday Plus Semi Synthetic 10W-40 or 15W-40 are commonly used across petrol and diesel vehicles, while Penrite Semi Synthetic 5W-40 suits drivers wanting extra protection without stepping into full synthetic territory. This type of oil strikes a good balance for many Australian conditions.

Full Synthetic Oil

Full synthetic oils are designed for modern engines, turbocharged vehicles, and performance setups. They handle high heat better, flow faster on cold starts, and provide the highest level of engine protection under load.

A good example is Penrite Full Synthetic Enviro+ 10W-40 Engine Oil, which is well suited to modern petrol and diesel engines that see mixed driving, towing, or higher operating temperatures.

Match the Oil to How You Drive

Your driving habits matter just as much as the engine design.

For daily commuting, a full synthetic or quality semi-synthetic oil is usually the best choice. Lighter grades like 0W-20 or 5W-30 flow quickly on cold starts, which helps reduce engine wear when the vehicle is only driven short distances and doesn’t always reach full operating temperature. These oils also support better fuel efficiency in stop-start traffic.

For performance, full synthetic oil is strongly recommended. Grades such as 5W-30, 5W-40, or 10W-40 are commonly specified, depending on the vehicle. These engines generate higher temperatures and tighter tolerances, and full synthetic oils are designed to maintain stable viscosity, resist breakdown, and protect critical components like turbochargers under load.

For 4WDs and towing, full synthetic or heavy-duty semi-synthetic oils are the most suitable. Heavier grades like 10W-40 or 15W-40 are often preferred, as they provide stronger oil pressure and protection during sustained loads, off-road driving, and high-temperature conditions. These oils are built to handle the extra stress that comes with towing and touring.

Don’t Forget Oil Change Intervals

Even the best engine oil needs regular replacement. How often you change it depends on the oil type and driving conditions.

General guidelines:

• Mineral oil – every 5,000–7,000 km
• Semi-synthetic oil – every 7,000–10,000 km
• Full synthetic oil – every 10,000–15,000 km

Harsh use like towing, off-road driving, short trips, or heavy traffic can shorten these intervals by 20–30%. Diesel engines may also need more frequent changes due to higher soot levels.

Choosing Oil Made Easy at Superspares

At the end of the day, choosing the right oil comes down to your vehicle’s specs, your driving style, and local conditions. If you’re unsure, Superspares makes it simple. As a trusted Australian car parts store, we stock quality engine oils suited to passenger cars, performance builds, and 4WDs, all matched to your vehicle. With expert support, fast delivery, and easy returns, keeping your engine protected is straightforward.