What will happen if I put 5W-30 instead of 5w20?
Your engine’s oil specification is chosen for a balance of startup performance, protection, and fuel economy. If your manufacturer calls for 5W-20 and you use 5W-30 instead, the effect is usually small but not always negligible. In many cases you won’t cause immediate damage, but you may notice changes in efficiency, engine feel, or oil pressure, and it may not be ideal for warranty or long-term wear.
What the numbers mean
Oil grades like 5W-20 and 5W-30 are multi-grade viscosities. The "5W" part indicates cold-start flow (the same winter rating for both), while the second number shows viscosity at operating temperature; a higher number (30 vs 20) means thicker oil when hot. The exact performance depends on the brand’s formulation, but in general, 5W-30 is thicker than 5W-20 at typical engine operating temperatures.
Viscosity explained
The first part of the grade (the number before W) reflects how the oil behaves in cold weather, affecting startup lubrication. The second part (the number after W) reflects how thick the oil is at engine-running temperatures, which influences film strength and wear protection. Engines designed for 5W-20 typically rely on a lower high-temperature viscosity to improve fuel economy, while 5W-30 provides greater film strength in hotter or heavier-load conditions.
Practical effects of using 5W-30 in place of 5W-20
The following points describe common outcomes you might notice if you run 5W-30 instead of the recommended 5W-20. This list is not universal; it depends on your engine design, climate, and how the oil is formulated by the brand.
- Fuel economy and performance: Slightly higher friction can reduce fuel economy by a small margin, and you might feel a marginal change in throttle response or acceleration.
- Oil pressure and flow: Thickened oil at operating temperature can raise reported oil pressure a bit, which may show up as higher readings on some gauges or dashboards, though most modern systems accommodate a range of viscosities.
- Lubrication under hot or heavy loads: In hot climates or under heavy towing/loads, 5W-30 can provide stronger lubricant film, potentially offering better protection than 5W-20 in those specific conditions.
- Cold-start behavior: Since both grades share the same 5W winter rating, cold-start flow is typically similar; you won’t gain a significant cold-start advantage using 5W-30.
- Seal and gasket stress: In engines with very tight tolerances or aging seals, a noticeably thicker oil could aggravate leaks or seepage in some rare cases, though 5W-30 is not dramatically thicker than 5W-20.
- Warranty and manufacturer guidance: Using a non-specified oil can complicate warranty claims if a failure is suspected to be related to lubrication; always verify with the manual or dealer.
In practice, most modern engines designed for 5W-20 can tolerate 5W-30 without catastrophic consequences for a short period, but it isn’t guaranteed to be beneficial and may not be covered under warranty if not approved by the manufacturer.
When it might be acceptable or recommended
There are scenarios where a manufacturer may allow or even recommend a heavier grade like 5W-30. Consider these conditions and guidance.
- OEM-approved alternatives: Some engines list 5W-30 as an acceptable alternative in certain climates or operating conditions. If the owner’s manual or dealer confirms this, you’re within specifications.
- Hot climates or heavy loads: In regions with high temperatures or for vehicles that regularly tow or carry heavy loads, 5W-30 can offer stronger protective film at operating temperature.
- Older engines or wear conditions: In some older engines with valve train wear or higher oil consumption, a slightly thicker oil can reduce leakage or oil burn-off; however, consult a professional because this is not universal and may mask underlying issues.
Always verify with the manufacturer or a trusted mechanic before deviating from the specified grade, even if you believe conditions warrant a change.
What to do if you’ve already filled with 5W-30
If you’ve already added 5W-30 when 5W-20 is specified, consider the following steps to minimize potential issues and stay within recommended guidelines.
- Check the owner’s manual: Confirm whether 5W-30 is listed as an acceptable alternative for your exact engine and model year.
- Monitor oil level and consumption: Watch for unusual consumption, leaks, or changes in oil pressure readings.
- Drive gently and avoid extreme conditions: If you notice any strange noises, reduced power, or warning lights, ease off and seek professional advice.
- Plan a return to the recommended grade: If advised, schedule an oil drain and fill with the factory-recommended viscosity as soon as practical.
In most cases, a single switch to 5W-30 is not dangerous if the engine is otherwise healthy and the manual permits it, but it’s best treated as a temporary measure rather than a long-term replacement for a specified grade.
How to choose the right oil for your car
Bottom line: follow your vehicle’s manufacturer specifications. If you’re considering a change for any reason, consult your owner’s manual, contact the dealership, or speak with a trusted mechanic. They can confirm whether a grade like 5W-30 is acceptable for your engine under your typical climate and driving conditions, and they can help you weigh any trade-offs in fuel economy, protection, and warranty coverage.
Summary
Using 5W-30 instead of 5W-20 is not universally harmful, but it is not universally beneficial either. The main difference is hot-temperature viscosity: 5W-30 is thicker at running temperature, which can offer better protection under high heat or heavy load, but can also reduce fuel economy and is not guaranteed to be compatible with every engine designed for 5W-20. Always verify with the owner’s manual or a trusted mechanic, and return to the specified grade if recommended. Regularly check oil level, pressure, and for leaks, and stay attentive to any changes in engine behavior.
