You check the dipstick, realise the oil level is low, and find a bottle of 5W-30 in the garage. The cap or owner’s manual calls for 0W-20. Can you use what you have?
Sometimes, yes..but only if the vehicle manufacturer permits 5W-30 for that engine.
It is tempting to assume the difference is minor because both are multigrade engine oils. But viscosity is only part of the specification. Before replacing a 0W-20 oil with a 5W-30 oil, check the manufacturer’s approved viscosity grades, required API, ACEA or ILSAC specifications, operating conditions and warranty requirements.
Key Point: Start with the manufacturer’s specification, then choose the viscosity.
What’s the Difference Between 0W-20 and 5W-30?
The numbers describe how an oil behaves at different temperatures.
The “0W” and “5W” ratings describe low-temperature performance. A 0W oil is designed to flow more readily at lower temperatures than a 5W oil.
The second number describes viscosity at normal engine operating temperatures. A 5W-30 remains thicker at operating temperature than a 0W-20.
| Factor | 0W-20 | 5W-30 |
| Cold-temperature rating | 0W | 5W |
| Operating-temperature grade | SAE 20 | SAE 30 |
| Relative hot viscosity | Lower | Higher |
| Can it replace the other? | Only when approved | Only when approved |
That does not mean 5W-30 automatically gives an engine “more protection.” Modern engines are designed around specific oil-flow characteristics, bearing clearances, oil pumps, turbochargers, and emissions systems. Thicker is not automatically better.
Can You Actually Replace 0W-20 With 5W-30?
It depends on the engine.
Some manufacturers list more than one acceptable viscosity grade, sometimes according to operating temperature or driving conditions. Others specify 0W-20 for a particular engine with few or no alternatives.
This is why choosing oil by viscosity alone can cause problems.
Two bottles labelled 5W-30 can also meet very different performance specifications. One may meet an ILSAC specification for a modern petrol engine, while another may be formulated around an ACEA specification and a completely different set of manufacturer approvals.
Do not assume every 5W-30 is interchangeable simply because the SAE grade on the bottle is the same.
Check These 5 Things Before Switching
1. Your Owner’s Manual
Start with the manufacturer’s oil recommendation. Check both the specified viscosity and any alternative grades listed for the engine.
If 5W-30 is listed as acceptable, switching may be possible. If only 0W-20 is specified, do not change grades simply because 5W-30 is available.
2. Required Oil Specifications
Look beyond the large viscosity numbers on the label.
Your engine may require an API, ACEA or ILSAC specification, plus an individual vehicle-manufacturer approval. The correct 5W-30 must satisfy the required performance level, not simply have the right viscosity.
This is visible across the LSA Oils automotive lubricant range, where different oils within similar viscosity ranges carry different specifications and applications.
3. Engine and Emissions System
Turbocharged petrol engines, hybrids and diesel engines fitted with particulate filters can place specific demands on engine oil.
For example, certain diesel particulate filter systems require low-SAPS formulations. Using an oil with an unsuitable additive formulation can affect the emissions system even when its viscosity appears correct.
4. Climate and Operating Conditions
A 0W oil offers stronger flow characteristics during very cold starts than a 5W oil.
That does not mean Australian drivers should automatically switch from 0W-20 to 5W-30 because the climate is warmer. Modern manufacturers consider far more than outside temperature when specifying an oil.
Use climate as one factor only when the manufacturer provides alternative viscosity options.
5. Warranty Requirements
For a vehicle still under warranty, check the service requirements before changing oil specifications.
Keep records of the oil used and confirm that it meets the specifications required for your engine. A bottle carrying the correct viscosity but the wrong performance specification may not satisfy those requirements.
What Could Happen if You Use the Wrong Viscosity?
One incorrect top-up does not automatically mean an engine will fail. The effect depends on the engine, oil specification, quantity added and operating conditions.
An unsuitable viscosity can, however, change cold-start oil flow, operating-temperature viscosity, fuel economy and lubrication behaviour. In some engines, using the wrong formulation may also be unsuitable for turbocharger or emissions-system requirements.
An engine may continue to operate normally with a different oil, but that does not mean the oil meets the manufacturer’s specified viscosity and performance requirements.
What if You Already Added 5W-30 to a 0W-20 Engine?
Do not assume damage has occurred.
If you used a small amount for a top-up, check the owner’s manual and compare the specifications of both oils. Determine whether 5W-30 is an approved alternative for that engine.
If an entire oil change was completed using an unapproved 5W-30, confirm the correct specification before continuing normal service. A workshop or lubricant specialist can also help identify whether the oil used is suitable.
How to Choose the Right Oil for Your Vehicle
Start with the vehicle manufacturer’s viscosity and performance specifications, then compare them with the product data sheet rather than relying only on the front label.
The LSA Oils Lube Guide can also be used to identify oils by application and then review the relevant product information, PDS and SDS documents before selection.
Frequently Asked Questions
Is 5W-30 thicker than 0W-20?
Yes. At normal operating temperatures, an SAE 30 oil has a higher viscosity range than an SAE 20 oil. Their cold-temperature ratings also differ, with 0W rated for lower-temperature performance than 5W.
Is 5W-30 better than 0W-20 in hot weather?
Not automatically. Some manufacturers allow alternative grades for particular temperature ranges, but outside temperature alone is not a reason to override the specified engine oil.
Can I mix 0W-20 and 5W-30?
A small emergency top-up may not cause immediate problems, but mixing oils changes the final blend. Check that both products meet the engine’s required specifications and return to the recommended oil at the appropriate service point.
Will using 5W-30 instead of 0W-20 damage my engine?
Not necessarily. Some engines approve both grades. Problems are more likely when the replacement oil falls outside the manufacturer’s specified viscosity or performance requirements.
Can I use 0W-20 instead of 5W-30?
Only if the vehicle manufacturer permits it. A lower-viscosity oil should not be substituted simply to improve fuel economy or cold-start flow. Check the approved viscosity range and required oil specifications first.
