Additive Clash

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Motor oils are "formulated" which is a fancy way to say that the engineers balance the ratios and types of additives added to base oils to get the effects they are trying to achieve. Mixing different "recipes" together can result in lower performing oils. An analogy would be mixing two different brands of yellow cake mix together to make a cake. It will come out of the oven looking like cake, but it may not be as good as either would baked separately.

That said, I have mixed brands of motor oil a bazillion times without noticeable ill effects to use up left over oil or to approximate the weight of oil I want if I don't have the right stuff on hand. My OBS Ford is running a mix of 0w-20 and 20w-50 as I was out of 5w-30 at the time. It won't notice the difference on the way to the lumber yard and back.
Exactly.
 

Astro14

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Might happen. might not.
Up to you…the only way to know is lab testing of the mix.

Personally, when I change brands, I stick with that brand to ensure compatible additive chemistry. I recognize that the first change has some leftover oil, and is thus a mix, but it’s a small percentage, perhaps 10-15% of what’s in the crankcase is old, but on subsequent changes, that’s minimized. I reckon 10-15% is small enough to minimize the concerns - a frankenbrew is a risk.
 

ATex7239

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Thanks for the comments and info folks. I’ll probably just start dumping the whole 5 qts in there and call it a day. A bonus jug after 10 or 12 changes isn’t really rocking my world…

But wait, what if I over filled it? What will that do? Oh god, when does it end!?!?
 

MolaKule

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So basically it’s doesn’t necessarily matter however it could matter but only if it does matter lol
Well, consider this: Each oil formula has a specific mix of base oils and additive package focused on a specific performance target. Any mixing of various brands may alter those performance targets in various ways.

This is especially true when adding third party aftermarket/OTS additives.
 
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Additive clash is something I am slightly worried about in my wife' CR-V. I used 4 qts of HPL Premium and a 1/2 qt of Amsoil SS, but I think it will be just fine with the .5 qt. I have 3 more qts but I wanted to keep it for my other car. That car will have a mix too. It will end up being 3 qts of HPL and 1.6 qts of "something". My options are M1 EP (I believe the old PAO blend), PUP or Kirkland.
 
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All I have to say on the subject, is that I have mixed weights, and brands, and switched brands almost every oil change, at various times over the years, in various makes of vehicles, and never had any adverse effects in any vehicle. Of course that is just me. But I use latest spec, or at least spec for the vehicle, and proper,(or thicker) viscosity, and change plenty often.
 
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Even
Additive clash is something I am slightly worried about in my wife' CR-V. I used 4 qts of HPL Premium and a 1/2 qt of Amsoil SS, but I think it will be just fine with the .5 qt. I have 3 more qts but I wanted to keep it for my other car. That car will have a mix too. It will end up being 3 qts of HPL and 1.6 qts of "something". My options are M1 EP (I believe the old PAO blend), PUP or Kirkland.
Even ignoring @High Performance Lubricants comment, why would you bother mixing HPL with anything? You’ll never realize the true benefit of HPL, not from a protection, performance, or lifespan time.

If my choice was to mix HPL or run a “mere” straight shelf-stock oil from WM, again- you’ve at least got a fully-formulated oil that will work as certified. You’ve got no real guarantees when “home-mixing”, yet if something negative were to happen some people would point the finger of blame at HPL since it’s not “certified”. If you spent 65-75% of the full cost on HPL (or any exceptionally crafted oil FWIW, claim all the benefits by going 100%. My .02…
 
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There is no requirement for compatibility between different brands of motor oil, and it is generally not recommended to mix different brands or types of oil. Mixing different oils may cause a chemical reaction that could result in a decrease in the performance of the oils, or could form a substance that could clog filters or damage engine components.

It is generally best to use the same brand and type of oil throughout the life of the vehicle, and to consult the owner's manual for the manufacturer's recommended oil viscosity and type.

If you do need to use a different brand or type of oil, it is generally recommended to drain the existing oil and refill with the new oil, rather than mixing the two.
It is also important to use the correct amount of oil as specified by the manufacturer, as using too little oil can result in insufficient lubrication and overheating, while using too much oil can cause the oil to foam, leading to reduced lubrication and increased wear on engine components.
 
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Even

Even ignoring @High Performance Lubricants comment, why would you bother mixing HPL with anything? You’ll never realize the true benefit of HPL, not from a protection, performance, or lifespan time.

If my choice was to mix HPL or run a “mere” straight shelf-stock oil from WM, again- you’ve at least got a fully-formulated oil that will work as certified. You’ve got no real guarantees when “home-mixing”, yet if something negative were to happen some people would point the finger of blame at HPL since it’s not “certified”. If you spent 65-75% of the full cost on HPL (or any exceptionally crafted oil FWIW, claim all the benefits by going 100%. My .02…
It wasn't my first choice to mix but I only bought 12 qts. With 3 cars, I need ~13.9. Wanting to have a few quarts left for my Impreza I was left with using what I had left over for her car which ended up being that half qt of amsoil, which is all the Amsoil SS 0W-20 that I had left. Had I chose to use HPL for that last half qt it would have left me with 2.5qt for the Impreza which takes 4.6 total. I "feel" that having 3 qts of HPL as the majority of oil in that sump that I'm still getting the cleaning benefits. I just need to decide which oil I have left will be the best fit with the HPL. I don't run extended drains in any of the cars. I also have a stash of oil. I just started using PUP for the Impreza but M1 EP prior. I have been using M1 EP exclusively in the Legacy prior to the HPL. Both Subarus are under warranty so I do the 6month/6k mile change. My wife's car is out of warranty with 134k miles. I go by the MM on that car and I usually push it down to ~5% though with the Amsoil I did run it down to like -2000 once. Probably won't do that again. These cars need to run as long as I can so frequent changes if fine with me. Now, if this was my S4 and I was still driving it I would consider doing HPL exclusively once i get through the stash of M1 I have. That car is in a different league from the others so I am cool with using a high performance oil for performanceand protection for a longer period of time.

Also, financially I have spent a lot of money the past few months so dishing out more money for another 6 pack wasn't really in the cards. A lot of the money was on car stuff too like a gallon of Amsoil ATF and a the spill and fill that went with it plus filter, rear brake replacement, 2 sets of tires and 2 aligments. And that doesn't include xmas gifts nor Scotch (probably spent as much on Scotch as I did the 2 cars 🤫). So, I had to make due with what I was able to get and have.

I agree with using 1 oil but in my case I had to make the best decisions I could with what I was able to buy.
 

OVERKILL

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This. Very small changes can return measurable differences in results. It is always best to avoid mixing oils. It’s not likely you will blow anything up. It’s also likely that a mixture could provide a lower performing product than what each would do individually.
Yup, that's my position on the matter as well. You are far more likely to produce a product that performs worse than the individual products that you are mixing than one that performs better.
 

ATex7239

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It is also important to use the correct amount of oil as specified by the manufacturer, as using too little oil can result in insufficient lubrication and overheating, while using too much oil can cause the oil to foam, leading to reduced lubrication and increased wear on engine components.
Are you referring to my comment about the 4.5 quarts on 4.8 or just in general? Between the dots the normal range. 2/3 in the normal range is fine. I don’t believe engines are that sensitive.
 
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Might happen. might not.
Up to you…the only way to know is lab testing of the mix.

Personally, when I change brands, I stick with that brand to ensure compatible additive chemistry. I recognize that the first change has some leftover oil, and is thus a mix, but it’s a small percentage, perhaps 10-15% of what’s in the crankcase is old, but on subsequent changes, that’s minimized. I reckon 10-15% is small enough to minimize the concerns - a frankenbrew is a risk.
How is a frankenbrew a risk?
 
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How is a frankenbrew a risk?
An oil manufacturer gave the board a direct response earlier in this thread. Considering that a majority of viewers on this board will never pony up for their products, it’s as close to an unbiased opinion that we’re likely to get. They’re simply not in competition with 99% of the brands that will ever be utilized in Frankenbrews.

Is “success” as determined by not causing engine failure probable? Yes. Are there unintended consequences that could start a chain reaction of bad things in your engine? Probably. As some have pointed out, each manufacturer’s oil is certified in its 100% concentration. Not one single mix is technically certified. Caveat emptor 👍🏻
 

Astro14

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How is a frankenbrew a risk?
Because it increases the risk of additive clash.

The great the degree of mixing, the greater the risk of additive performance degradation through negative interaction. So, the higher the percentage of adulteration, the greater the degradation.

Multiple additive packages in one mix increases the chances of negative interaction.

So, the frankenbrew, a mix of several oils, has the highest risk of all, through multiple additive packages, with increased opportunity for negative interaction, and a higher degree of adulteration on each oil type.
 

ATex7239

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So it sounds like to put it succinctly it is best to stick with one oil if at all possible. However it is OK to use different oils just don’t go out of your way to erroneously mix them. If you’re going to swap around for whatever reason just change out all of it.
 
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