can you put 10w30 oil in a 5w30 car

[SanCamila]

Putting 10W-30 oil in a car that specifies 5W-30 is generally not recommended. While the engine will likely run without immediate failure, you risk reduced fuel efficiency, poorer cold-weather starting, and potential long-term wear. The key difference lies in the oil's viscosity, or resistance to flow. The first number (5W or 10W) indicates the oil's flow at cold temperatures (W for Winter). A 5W oil is thinner and flows more easily at startup than a 10W oil, ensuring critical engine parts are lubricated faster. Using a thicker 10W oil in cold climates can mean your engine runs with inadequate lubrication for a longer period after ignition.

The second number (30) is the oil's viscosity at operating temperature (100°C). Both oils have the same "30" rating, meaning they provide similar protection once the engine is fully warmed up. This is why some people believe the oils are interchangeable. However, the compromise in cold-start protection is significant. Modern engines with tight tolerances are designed for specific oil viscosities to optimize performance and longevity. Deviating from the manufacturer's recommendation can also affect your vehicle's warranty coverage.

For most drivers, the potential downsides outweigh any perceived benefits. Stick with the 5W-30 specified in your owner's manual for optimal protection, especially if you experience cold winters. The only scenario where a temporary switch might be considered is if you're in a pinch and 5W-30 is unavailable, but you should change back to the correct oil as soon as possible.

Characteristic	5W-30 Oil	10W-30 Oil	Why It Matters
Cold-Temp Viscosity	Thinner, flows easier	Thicker, flows slower	Faster lubrication on cold starts, reducing engine wear.
Cold-Weather Starting	Easier, less strain on battery	More difficult, increased battery load	Critical for reliable operation in winter climates.
Fuel Economy Impact	Minimal negative impact	Can reduce fuel efficiency	Thicker oil requires more energy for the engine to pump.
Engine Wear Protection	Optimal for engines designed for it	Suboptimal cold-start protection	Adhering to specs ensures long-term engine health.
Manufacturer Warranty	Maintains compliance	Potential risk to coverage	Using the wrong oil can void powertrain warranties.

[LaFelix]

As a mechanic, I've seen this a lot. You can probably get away with it for a short time if you're desperate, but I'd never recommend it for the long haul. That thicker 10W oil is harder for your engine to pump on a cold morning. It's like trying to pour cold maple syrup versus warm syrup. That extra few seconds without proper lubrication on startup is where most engine wear happens. Stick with the 5W-30. It's what your engine's engineers designed it for.