What happens if you put 0W20 in car that uses 5W-20?
In most cases, pouring 0W-20 into an engine that specifies 5W-20 won’t cause immediate damage, but it isn’t automatically approved by all manufacturers. The key difference is cold-start flow: 0W-20 is thinner at low temperatures, while both oils typically share the same hot-viscosity when the engine is warm. Always check the owner's manual or with a dealer to confirm acceptable oil grades for your vehicle.
To understand what this means for your car, it helps to know how multi-grade oils are rated and why manufacturers pick specific grades. The “W” stands for winter (cold-temperature performance), and the second number indicates viscosity when the oil is hot (at about 100°C). An engine that calls for 5W-20 expects a certain protective film as it warms up; a 0W-20 oil will flow more readily when starting cold, but generally aims for the same 20 weight at operating temperature. The practical effect depends on climate, driving conditions, and the engine design.
Understanding oil viscosity and grade choices
Oil viscosity is a measure of how thick or thin the oil is at a given temperature. The “W” rating means the oil remains pliable enough to pump and lubricate during cold starts, while the trailing number (20 in this case) represents the oil’s viscosity when the engine is at normal operating temperature. Modern engines rely on a precise oil film to protect moving parts, especially on startup and under heavy loads. While 0W-20 and 5W-20 share the same hot-viscosity rating, their cold-flow characteristics differ, which can impact startup wear and fuel economy in different climates.
Why some cars explicitly require 5W-20
Manufacturers specify a grade based on engine tolerances, oil-pressure targets, and intended climate. Some engines are tuned to run with a specific cold-start performance that a 0W oil may not meet, even if the hot-viscosity matches. In other cases, automakers test and certify oils against particular specifications (API, ILSAC, or OEM approvals), and using a different grade could affect warranty coverage or long-term wear characteristics.
Substituting 0W-20 for 5W-20: what to expect
Here is what typically happens if you use 0W-20 in an engine that calls for 5W-20. The following points summarize practical outcomes you might notice or consider.
- Easier cold starts and faster oil circulation in very cold weather. This can reduce startup wear in frigid climates.
- Similar lubrication performance once the engine is at operating temperature, because both grades target a 20 cSt-like viscosity at 100°C.
- Potentially lower oil pressure readings on startup in some engines that are designed around a specific cold-start behavior or tighter tolerances.
- Possible small gains in fuel economy due to lower viscous drag in certain driving conditions, though the difference is usually modest.
- Warranty or service restrictions if the manual specifies 5W-20 only or if OEM approvals do not include 0W-20 for your model.
In practice, the difference between 0W-20 and 5W-20 is often minor once the engine is warm. The most important factor is ensuring the oil meets the same overall specifications (such as API SP or ILSAC GF-6, plus any OEM approvals) and that the grade is listed as acceptable in your manual. Climate and driving style will also influence whether you notice any change.
Before making a switch: considerations and precautions
Before opting to use 0W-20 in place of 5W-20, consider these guidelines. They help determine whether the substitution is appropriate for your vehicle and circumstances.
- Check the owner’s manual or manufacturer’s technical bulletins for approved oil grades. Some engines explicitly require 5W-20 only.
- Ensure the 0W-20 you select meets the same API/ILSAC certification and OEM approvals as the 5W-20 recommended for your car.
- Consider climate and typical operating temperatures. Very cold climates can benefit from 0W-20, while very hot climates may see negligible or negative effects if the grade isn’t approved.
- Be mindful of warranty implications. Using a non-approved oil grade can affect coverage if a failure is claimed to be related to lubrication.
- Monitor for unusual symptoms after a change, such as oil pressure warning lights, strange engine noises on startup, or changes in idle behavior.
Ultimately, the safest course is to use the oil grade specified by the manufacturer. If you’re considering 0W-20 due to availability, cost, or climate, verify with the dealer or consult the vehicle’s service bulletin to confirm compatibility.
What to do if you already poured 0W-20
If you accidentally filled with 0W-20 and your manual calls for 5W-20, you should plan to revert to the recommended grade at your next oil change. In many cases, driving a short distance to reach a service location is fine, but avoid prolonged use if you notice abnormal oil pressure readings, engine noises, or warning lights. Keep receipts and documentation showing the oil grade used, in case warranty questions arise.
Summary
Using 0W-20 in an engine that specifies 5W-20 is not automatically harmful, but it is not universally approved. The main difference lies in cold-start performance, with 0W-20 flowing more readily at low temperatures, while hot-viscosity remains similar. For most drivers, the engine will operate normally if the oil meets the same certifications and the vehicle’s manual allows the substitution. The best practice is to follow the manufacturer’s recommended grade, consider climate and driving conditions, and consult a dealer if you’re unsure. Always verify oil compatibility to protect warranties and engine longevity.
Is it okay to mix 5W and 0W oil?
Adding 0.5 quart of 5w30 to 4-5 quarts of 0W20 will change nothing. He will still have 0W20 blend in the sump. It will increase oil viscosity very little but oil most likely will still remain in cold and hot viscosity ranges of 0W20.
What happens if I put 0W20 in a car that takes 5w20?
The 0W or 5W refers to the pumpability in cold temperatures. Therefore, a 0W would flow more easily than a 5W and could be an acceptable substitute. Thus, it is suitable to use a SAE 0W-20 as a replacement for SAE 5W-20 application.
Is there a big difference between 5w20 and 0W20 oil?
0W-20 and 5W-20 are the exact same viscosity. The important number is the weight, after the hyphen. The only difference is how easily it flows in colder conditions before the engine reaches optimal temperatures. The thickness, or weight, at operating temperature is going to be the same for both oils regardless.
What happens if you put a little bit of the wrong oil in your car?
Use only what the owner's manual specifies. Using the wrong oil can lead to reduced lubrication and shorter engine life. If the manual says to use synthetic oil, do so. Contrary to what some believe, adding synthetic oil to regular oil won't harm the engine, but there's also no benefit in doing so.
