Could you mix two different number engine oils of same brand to one car?

[rc5]

My car was using 10W30. Since the winter is coming, I want to use thinner oil. Can I buy 5w30 of same brand and add it to my engine without doing an total oil/filter change?

 

[Generalen]

I would not mix old oil with new oil, I think it says something about that on the oilcan. "I don't think it's so good for the engine." And the new oil will have a much shorter lifespan.

 

[veryape]

Don't be ridiculous. Of course you can add oil without changing it, I mean what the heck do you think you do when you are a quart low, change the oil? Of course not you add a quart. Also, different viscosities will not hurt anything either.

 

[woodie1]

What you wish to do will work fine. It doesn't have to be the same brand oil, just the same SAE Spec.

 

[Thump553]

Do NOT mix different weight oils. Probably should change the oil completely as part of your winterizing (be sure to check hoses and belts, too).

Rather than asking the question on an internet BBS, and probably getting all sorts of unqualified answers, why don't you read your owner's manual.

 

[amdskip]

change it before changing weights

 

[apoppin]

I mix synthetic and conventional oils of the same weight and brand.

I am not sure of mixing different oils of the same viscosity. Let's see, the -w30 remains the same. The only addition you are making is a change from 10w- to 5w-.

I'd really like to see something other than opinion as to why this would be bad.

EDIT: If you absolutely want to be safe, change the oil and filter. It is SO cheap. It seems to me that it must have been a few months since your last OC anyway. This way, the change should last you through the cold spell till the next one.

Why are you quibbling about $10-$20? It is much cheaper to change your oil every 3K miles than your engine.

 

[Zenmervolt]

I don't think it would be bad, but I'm not an expert in that particular area. I have to ask though, how could you add enough oil to make a difference in viscosity without changing the oil? Assuming your car does not burn oil, it should remain roughly full throughout the entire oil change interval. If you add enough oil to have a significant effect on the viscosity, it seems to me that your engine would then be rather severely overfull of oil, which can lead to blown seals or, in a worse case scenario, damage to smaller portions of the oil delivery system due to excess pressure. Given the price of an oil change, I would think that it would be better to simply have the oil changed and use 5w30. I'm making these assumptions based on my 202,000 mile Accord, which uses far less than one quart of oil between oil changes (approx. 3,000 miles).

Zenmervolt

 

[Soybomb]

As it has already been pointed out you'd be fine. But I too must ask why? If you're wanting to make the oil thinner you need more than 1/2 of a quart of 5w30. Couldn't you use an oil change anyway?

Or you could just use Mobil1 10w-30 synthetic all year.....ohh synthetic oils pour sooooo well even when cold

 

[mackdawgson]

I'm just happy as long as there is ANY oil in my car. Of course I don't have a nice car...

 

[cipher00]

I wouldn't. Agree with above: get an oil change.

 

[Cyberian]

<< Do NOT mix different weight oils. >>


Why not?

 

[rc5]

Yeah, there's some oil leakage of this old car and I don't bother to fix it. Why don't I do a full oil change? Because I just did one a week ago with 10w-30 oil.

 

[apoppin]

<< Yeah, there's some oil leakage of this old car and I don't bother to fix it. Why don't I do a full oil change? Because I just did one a week ago with 10w-30 oil. >>



A week ago? Good planning . . . Winter comes about the same time every year.


Is there ANY reason NOT to mix oils of the same brand but different viscosity?
(I don't see why not).

EDIT: For minimum work and maximum effect with least cost, just drain out the 10w-30 oil and refill 5w-30 oil WITHOUT changing the filter (since it was only a week ago). If your are REALLY thrifty and your pans are clean, you can SAVE the 10w-30 oil till next spring (but don't forget the change the filter then).

 

[Viperoni]

I always mix oils......
I get a 10w-30 oil change and in the summer I add 20w-50 or at least 10w-40, in the winter I add 5w-30.......my 86 parisienne with a 305 chevy has 310k kilometers and still leaves rubber