My New car says it takes 5w-20 and I just accidentally put 5w-30 in my car... now I'm worried.

I heard that 5w-0 is used in the winter because it has a lower viscosity which allows the fluid to move easier in the winter, and 5w-20 is used in the summer because the ambient temperature loosens up the viscosity?

What does the 5w stand for and if my car says to use 5w-20, is it safe to use 5w-0 in the winter and 5w-30 in the summer

I just dont want to damage anything.

2 Answers 2


Just change the oil to 5W-20. You'll have caused no damage. The heavier weight oil will have just caused a little worse gas mileage. It can also affect how variable valve timing may be working if your vehicle is equipped with it. However, as soon as you change back to the correct weigh, all should be well in Whoville.

"5W" relates to how oil flows (its viscosity). This means, when it's cold, it will flow as though it is 5W, though it is actually still a 30 weight oil (or 20 weight oil or whatever happens to be the second number). You state "5W-0" in your question. To my knowledge, there's no such thing. The second number will always be higher than the first in multiweight oil, because the first is how the oil behaves when cold. The second number is the actual weight of the oil. I'm wondering if what you saw was 0W-20 oil.

As far as what oil to use when, you can never go wrong with using the weight of oil the manufacturer states. You can usually find this information in your owner's manual.


I have had a car that takes 0W-20 since 2011 (or well, actually, I have had two cars). At the dealership, they sometimes put 5W-30 oil there. I don't understand why since the manufacturer of the car has specified 0W-20, and not 5W-30.

My experience is that 5W-30 when put to a car that takes 0W-20 oil does not cause any engine damage. Also, I used to have a really old car that took 5W-30. Well, sometimes some oil change guys put 5W-50, thinking that since it's an old car, let's put some really thick oil in. Even that 20-unit difference caused no damage.

SAE 20 means 5.6 - 9.3 cSt and SAE 30 means 9.3 - 12.5 cSt viscosity @ 100 degrees Celsius. So, as you can see, a thick SAE 20 can actually be equal to a thin SAE 30.

The 0W vs 5W means the 5W oil will be harder to start in the extreme cold (such as -20 degrees Celsius). The -30 part is more worrying, meaning its viscosity is larger than -20 oil. It causes more fuel consumption. In theory, the additional viscosity could affect how the oil flows around the engine.

I wouldn't change the oil immediately after putting 5W-30. I would just keep on driving with the 5W-30 and then at the next oil change, use the correct grade (0W-20).

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