How bad is it to use 5W-30 instead of 5W-20 in a car?

Question

I have a 2008 Dodge Grand Caravan. The oil cap states that the engine is to use 5W-20 oil. I just realized that when we had our oil changed a few weeks (months? hard to remember) ago, it seems the engine was filled with 5W-30. At least, that's what the little sticker says that the shop put in the upper corner of my window - they may have used the right stuff and wrote it down wrong.

Two questions:

1. Is this a big deal to have happen once? As in, can I just leave it be and make sure the right oil is used next time? (FWIW, I live in Virginia.)

2. Would this cause my Check Oil light to come on? It just did today, though it seems that that I'm not low on oil.

Answer 1

Overall, if it was the wrong weight oil, it isn't too big of a deal. Having oil is the most important thing :o) Having the heavier oil in it shouldn't have caused any wear or be detrimental to the longevity of the engine.

There are some things it might affect. If the vehicle in question has variable cam timing (I'm betting it does), the oil weight can affect how well it works.

The weight of the oil (if thicker) can make it harder to push oil through your system, which soaks up a little bit of power and can cause a little worse gas mileage. Both of these things go back to normal with the correct oil weight.

Since the oil light has come on, I think it'd be a good assumption the oil light may have had something to do with it. I'd suggest you might want to get it changed as soon as possible. This would allow you to understand if the oil weight has something to do with it, or if you have other issues going on.

There may be some other things which I'm forgetting. While it's not a good thing in modern engines to use the wrong weight oil, it shouldn't have caused any long lasting issues.

Answer 2

I have had that done several times in a new 2011 Toyota Yaris I bought (I sold it in 2016).

The car manual clearly stated that 5W-20 oil should be used, but the dealership sometimes for some strange reason put 5W-30 oil in there.

I didn't notice any additional fuel consumption. Most likely the 5W-30 oil caused slight additional fuel consumption but it was lost in the noise.

No engine damage or excessive oil consumption either during my ownership period. For fun, in summer 2022 I googled for the registration number of my car and I saw it was for sale again, at a quite high asking price indeed. So I suspect it didn't suffer any damage from the use of 5W-30 oil in the long run either.

The 2011 Yaris had variable cam timing both on intake and exhaust side. I wasn't aware of any problem in that mechanism due to incorrect oil weight.

You might want to inform the oil change place of the correct oil specifications next time you change the oil. Weight isn't the only one. For example, my current 2016 Toyota RAV4 hybrid requires not only 0W-20 but also ILSAC GF-5.

However, if the oil light is on, you should do something about it. Either it's a yellow oil level light (in that case check oil level, if you already checked it then putting correct weight oil in there is a good next guess), or a red oil pressure light (in which case you should have the car immediately towed for repair). But if it's a maintenance reminder message or light, in that case it may just need resetting which the oil change place didn't probably do.