Which oil is better for summer 5W-30 or 5w40?
For summer driving, there isn’t a universal “better” option; the right choice depends on your engine and climate. In many modern engines, 5W-30 is the standard summer grade, while 5W-40 can offer extra high-temperature protection if your manufacturer allows it.
This article explains the key differences between 5W-30 and 5W-40, how heat affects oil performance, and how to decide based on your vehicle’s specifications, driving conditions, and climate.
Understanding viscosity and heat
Both 5W-30 and 5W-40 are multi-grade oils that flow well at cold temperatures (the “5W” part) and differ in their high-temperature viscosity (the “30” vs “40” part). The higher second number means the oil stays thicker at operating temperatures, offering greater film strength and protection under heat and heavy loads, but potentially reducing fuel economy slightly and sometimes affecting oil consumption.
What the numbers mean for summer performance
In hot conditions, a higher high-temperature viscosity like 5W-40 can help maintain oil film strength on hot engine parts (bearings, cams, turbochargers). If your engine is designed for 5W-30, using 5W-40 can still be acceptable when approved by the manufacturer, but it may not deliver meaningful benefits in every situation. Conversely, 5W-30 is typically chosen for better fuel economy and quicker lubrication on startup, and it suits many engines designed around that spec.
Practical considerations for summer choice
Before selecting a grade for summer, consider these factors to guide your decision.
- Manufacturer specification and warranty: Always check the owner's manual for the approved viscosity and any notes about alternatives. Using a non-approved grade could affect protection and warranty.
- Ambient temperatures and climate: In very hot climates (high daytime temperatures for extended periods), 5W-40 may offer better protection if allowed by the manufacturer; in milder heat, 5W-30 is usually adequate.
- Engine design and condition: Turbocharged, high-load, or high-mileage engines may benefit from 5W-40 if the OEM allows it; modern naturally aspirated engines often run perfectly well on 5W-30.
- Driving patterns: Frequent long highway trips or towing in heat can push oil temperatures higher, where 5W-40’s thicker film may help; city driving with moderate heat may not require it.
- Oil type and quality: Synthetic oils tend to maintain viscosity better in heat and offer more consistent protection than conventional oils; ensure the oil meets the correct API/ACEA and OEM spec.
- Fuel economy and oil consumption: 5W-30 generally yields slightly better fuel economy and may burn less oil in some engines; the actual difference is engine-dependent.
Concisely, follow the manual: if it specifies 5W-30, stay with it; if it allows 5W-40 and you operate in hot conditions or under heavy load, 5W-40 can be a reasonable option when used as approved by the manufacturer.
Bottom line and maintenance tips
Always verify the correct grade and specification with your vehicle’s documentation and trusted service provider. If you switch grades, ensure the oil meets the required specifications (for example, a specific API/ACEA rating or OEM specification). Regular oil changes with the right oil type remain the best defense against heat-related wear.
Summary
There is no one-size-fits-all answer. 5W-30 is the common summer-grade in many modern engines and can deliver excellent protection and fuel efficiency when specified. 5W-40 offers stronger protection at higher temperatures and under heavy loads, but only if the manufacturer approves its use. The safest approach is to follow the vehicle’s manual and consult a trusted mechanic if you’re considering a switch due to unusually hot climates or demanding driving conditions.
