Mixing viscosities and or brands OK or NO?

[SugarMouth]

I have read through many threads on this subject. I am still unsure if this is an acceptable practice. Leaving warranties out of the conversation, is it OK to mix viscosities and or brands of oil.

Example:

Mix Pennzoil Platinum Euro L 5W-30 with Kirkland Full Synthetic 0W-20.

or

Mix Valvoline European Vehicle Full Synthetic 5W-40 with Kirkland Full Synthetic 5W-30.

I still don't have a clear understanding if it is safe to do so.

Thanks!

 

[tblt44]

You will make a 2.5W 25
Or a 5w 35
Mix anything it no mada

 

[walterjay]

Mix away.

 

[PimTac]

This reply from Astro14 in the other current thread on this same subject is a pretty definite answer.

..

“Miscibility is one thing (you can mix them and they won’t separate out).

But weird, unpredictable things can happen when different additive chemistries are mixed. Changes in cold performance. Foaming. Lowered resistance to oxidation. So, sure, they mix okay, but they may not work well together.

I know, you’re always mixing a tiny bit when you change oil, but the leftover bit is a lot smaller than a whole quart of top off oil.

Personally, I prefer to top off with the identical brand and spec. E.G. Using Castrol 0W40 in the Volvo? It gets topped off with the same jug. And the next oil change will be the same Castrol 0W40.

Mixed is probably better than a quart low, and certainly better than very low.

But mixed is not as good as unmixed.”

 

[JavierH19]

In simple terms it's perfectly fine in the extreme majority of engines.

 

[JeffKeryk]

Every manufacturer and oil container label states specifically not to ever mix anything. Ever.
Right?

Trillions of miles have been driven on Frankenbrews. I am running one in our Lexus GS350 F Sport.
And so is everyother car that is not running the factory fill.

 

[RooflessVW]

It's "safe" but I don't see the point

 

[SugarMouth]

It's "safe" but I don't see the point

My curiosity is because I'll end up with a bunch of containers with a quart or so of oil left in them from different brands.

 

[ATex7239]

Every manufacturer and oil container label states specifically not to ever mix anything. Ever.
Right?

Trillions of miles have been driven on Frankenbrews. I am running one in our Lexus GS350 F Sport.
And so is everyother car that is not running the factory fill.

But, but, but, what if something could potentially maybe possibly happen....

 

[JeffKeryk]

It's "safe" but I don't see the point

To me, the point is to have sufficient oil in the crankcase.

 

[NormanBuntz]

Perhaps one way to minimize the possible negative effects of "mixing" is to use the mix for a shorter interval, like 3,000 miles.

 

[SwampSurvivor]

Isn't part of the API certification that it can be mixed with another oil of the same API class oil without negative affects?

 

[71Chevyguy]

As long as the end result isn't thinner than what is recommended for your engine, you should be fine. Just don't use a mixture like this to try a 15-20k run. It is no longer optimal for super long runs because of mixing the different formulas. But if you are keeping it reasonable, you should be just fine.

 

[edhackett]

Every manufacturer and oil container label states specifically not to ever mix anything. Ever.
Right?

Trillions of miles have been driven on Frankenbrews. I am running one in our Lexus GS350 F Sport.
And so is everyother car that is not running the factory fill.

Here's what Mobil has to say on the subject:

In general, oils should be compatible with each other. It is not likely that you would form gel by mixing the two oils. However, we would not recommend mixing oils as a general practice because oils are complex mixtures of additives and base oils that can be destabilized.

Mixing synthetic with conventional oil | Mobil™

In general, oils should be compatible with each other. It is not likely that you would form gel by mixing the two oils.

www.mobil.com

Ed

 

[joegreen]

I have read through many threads on this subject. I am still unsure if this is an acceptable practice. Leaving warranties out of the conversation, is it OK to mix viscosities and or brands of oil.

Example:

Mix Pennzoil Platinum Euro L 5W-30 with Kirkland Full Synthetic 0W-20.

or

Mix Valvoline European Vehicle Full Synthetic 5W-40 with Kirkland Full Synthetic 5W-30.

I still don't have a clear understanding if it is safe to do so.

Thanks!

Short answer is yes. Many people top up there oil with whatever they have lying around.

 

[OS4A]

From frankenbrew thread

 

[doublebase]

I’ll be throwing a frankenbrew into my Avalon in a couple months, simply because I have a lot of oil left over, but I wouldn’t normally do this. But one oil change for 5,000 miles? I’m not too concerned. The brew will be Pennzoil platinum, Amalie, Amsoil, Shell Rotella Gas Truck and I think Quaker State. I believe all of it is either 0w20 and 5w20.

The way I look at it regarding additives/mixing/etc, is that a lot worse “mixing” happens as soon as you turn on that engine and combustion happens...when those gases start blowing past those rings, and some of that fuel gets in there, or EGR gas, and moisture...or the silicates, and other things that get past the air filter. Then there’s whatever oil was actually left in the engine when you drained it...or whatever you use when topping up.

But I normally wouldn’t do this^.

 

[wwillson]

I used to think it was ok to mix different brands which have different add packs, base stocks, etc, until I talked to the chemists in HPL's lab. When I asked them this question, they said no, do not mix different formulations together and think everything will be ok in the crankcase. The only way you can possibly know if the oils will work well together is to test the frankenbrew in the lab. The main problem they see if foaming. They have seen a perfectly functioning engine oil that will foam like nobody's business when just a small amount of another additive is added. They have even see oil foam when an anti-foam agent is added! Additive clash is real and I needed no more convincing not to mix oils.

 

[GON]

Any issues on mixing Shell RGT 0w20 with Shell RGT 5w30 in equal amounts? I have a large amount of 0w20, prefer to run 5w30, although Ford recommends 5w20 for my 2002 F350 6.8L V10 with 200k miles. This truck sits a lot, but when it is run it typically has a 10k gooseneck behind it.

 

[ET16]

Isn't part of the API certification that it can be mixed with another oil of the same API class oil without negative affects?

This is my sense, too.