When it comes to 5W20 vs 5W40, many car owners get confused about which one works better. At Rapidwrench, We’re going to compare these two motor oil! And if you ever need expert help with oil changes, tune-ups, or any roadside issue, just call us at 1(866) 511-0898.
Viscosity Difference Between 5W20 and 5W40
Viscosity at operating temperature defines how thick or thin oil remains when your engine heats up.
5W20 has a viscosity of about 5.6 to 7.0 mm²/s at 100°C, making it lighter and thinner, while 5W40 comes in at 12 to 16 mm²/s at 100°C, giving it a stronger, thicker film. On the one hand, the thinner structure of 5W20 supports fuel economy. On the other hand, the thicker stability of 5W40 provides extra protection under heavy stress.
Engine Wear Protection in 5W20 vs 5W40
The thinner structure of 5W20 offers less resistance, which makes it smooth for newer engines with tight tolerances. However, 5W40 provides a 15–30% thicker protective layer under high heat, which is vital when towing, driving at high speeds, or using older engines with higher mileage. In contrast to 5W20, 5W40 is better suited for vehicles with over 100,000 km on the odometer.
Fuel Efficiency Difference Between 5W20 and 5W40
Fuel economy is where 5W20 stands out. Because it reduces drag inside the engine, it can improve mileage by 2–3%, saving about 0.1 to 0.3 liters of fuel per 10 liters consumed. Whereas 5W40 focuses more on durability than economy, meaning you get slightly lower mileage but stronger wear resistance.
5W20 Oil Change Interval vs 5W40 Oil change interval
Oil stability determines how long it lasts before breaking down. To put it simply, 5W20 generally needs to be replaced around 10,000–12,000 km, while 5W40 synthetic blends can stretch to 12,000–15,000 km thanks to better thermal resistance. In contrast, the extended stability of 5W40 means fewer oil changes over long-term usage.
5w20 Vehicle Compatibility vs 5W40 vehicle compatibility
Compatibility depends on what type of engine you’re driving. Many modern gasoline cars—especially with direct injection or turbo—recommend 5W20 because it works well with emission controls and fuel efficiency standards. However, diesel engines, SUVs, performance cars, and heavy-duty trucks lean towards 5W40 because of its extra stability in high-stress driving.
Cold Start Performance of 5W20 and 5W40
Cold mornings are tough on engines. Both oils share the same “5W” rating, meaning they perform well at -30°C. However, 5W20 flows faster in extreme cold, taking only 10–12 seconds compared to 14–16 seconds for 5W40. Because of this, drivers in colder states often notice smoother startups with 5W20.
Hot Climate Performance between: 5W 20 and 5W 40
High temperatures create the opposite challenge. 5W20 risks becoming too thin above 30°C, especially in desert or southern regions. By contrast, 5W40 holds its thickness up to 50°C, keeping engines safe during long highway drives or towing in summer heat.
Driving Style and Usage Scenarios
Every driving pattern tells a different story. For city driving and short trips, 5W20 delivers smoothness and efficiency. But when the vehicle is used for towing trailers, long-distance highway drives, or performance runs, 5W40’s thickness proves more reliable. In contrast to lighter use cases, heavy-duty driving strongly favors 5W40.
Longevity Difference Between 5W20 and 5W40
Engine life depends on balancing fuel savings and wear protection. While 5W20 supports modern cars by reducing friction, 5W40 prolongs life in older engines by filling larger clearances with a thicker film. As a result, the oil you choose can shape how your vehicle performs over years of ownership.
5W 20 cost versus 5W 40 price value
Price differences often play into the decision. On average, 5W20 oils cost slightly less than 5W40. But while you may save upfront with 5W20, you could end up changing it more frequently. In contrast, the durability of 5W40 can make it more cost-effective over long mileage, especially when driving in demanding conditions.
Final Thoughts
Choosing between 5W20 and 5W40 is not about which oil is “better” in general—it’s about which oil is better for your vehicle, your climate, and your driving style. If you value fuel savings, smoother starts, and have a newer car, 5W20 is often the winner. But if your car has high mileage, you tow, or you live in a hot climate, 5W40 is the smarter option.
At Rapidwrench, we’ve serviced thousands of vehicles across the U.S., and we know that the right oil makes a big difference in performance and peace of mind. If you’re unsure which oil is best, give us a call at 1(866) 511-0898, and our mobile mechanics will guide you, wherever you are.
FAQ
What is the main difference between 5W20 and 5W40 motor oil?
The main difference between 5W20 and 5W40 lies in viscosity, with 5W20 being thinner at operating temperature and 5W40 being thicker, which means 5W20 supports better fuel efficiency while 5W40 provides stronger protection under heavy loads.
Why do some vehicles recommend 5W20 while others suggest 5W40?
Because engine designs are different, manufacturers set oil recommendations based on clearances, performance needs, and emission standards, so smaller modern engines usually prefer 5W20 while larger or older engines perform better with 5W40.
When should I use 5W40 instead of 5W20?
To protect your engine under high heat, towing, or long-distance highway driving, 5W40 is often the better choice instead of 5W20, especially for older vehicles with higher mileage or for use in hot climates.
Which oil lasts longer before it needs to be changed, 5W20 or 5W40?
5W40 typically lasts longer before it breaks down, with oil change intervals around 12,000–15,000 km compared to 10,000–12,000 km for 5W20, which means you may get longer use between changes with 5W40.
Does 5W20 provide the same level of wear protection as 5W40?
5W20 does not provide the same level of high-temperature wear protection as 5W40, because its thinner film is designed for efficiency, while 5W40 leaves a 15–30% thicker layer on engine parts under stress.
Can I switch from 5W20 to 5W40 in my vehicle?
Yes, you can switch in some cases, but it depends on your manufacturer’s recommendation and your driving conditions, so Rapidwrench advises checking your manual or calling our experts at 1(866) 511-0898 before making a change.
Do 5W20 and 5W40 perform similarly in cold weather?
Yes, both oils perform similarly in cold starts because of the “5W” winter grade, but 5W20 flows slightly faster in extreme cold below -30°C, which makes startups smoother in very cold regions.
Is 5W40 better than 5W20 for high mileage cars?
5W40 is generally better than 5W20 for high mileage cars because its thicker viscosity helps seal worn engine parts and provides stronger protection for vehicles with over 100,000 km.
Which oil is more suitable for summer driving, 5W20 or 5W40?
5W40 is more suitable for summer driving in hot climates because it stays thicker at temperatures up to 50°C, while 5W20 may become too thin in extreme heat.
What happens if I put 5W40 in a car that requires 5W20?
If you put 5W40 in a car that requires 5W20, your engine may run slightly less efficiently, but it will likely be safe, and in some cases, the thicker oil may even help with protection in high-stress conditions.
Why is 5W20 often used in newer vehicles compared to 5W40?
Because newer engines are designed with tighter tolerances and stricter fuel efficiency targets, automakers recommend 5W20 more often, whereas older designs can handle the thickness of 5W40.
I want my car to last longer, should I pick 5W20 or 5W40?
If your goal is long engine life, 5W40 may be the safer pick for older or high-mileage vehicles, while 5W20 works well for newer cars, so the choice depends on your vehicle’s age and how you drive it.
Can Rapidwrench help me decide whether 5W20 or 5W40 is right for my vehicle?
Yes, Rapidwrench mobile mechanics can evaluate your vehicle type, driving style, and climate conditions to recommend the right oil, and you can get help right away by calling 1(866) 511-0898.