Mixing oils

[OVERKILL]

Originally Posted by ToadU
""Mobil 1 is fully compatible with conventional engine oils, semi-synthetic engine oils and other synthetic engine oils if you need to mix them.


See that last bit, if you NEED to mix them, like if you were at a gas station and down two quarts. Also per Mobil:

Originally Posted by Mobil 1
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. Also, why reduce the outstanding performance of Mobil 1â„¢ synthetic motor oils by adding "regular oil"? Is it economics? You would be better to run all Mobil 1 and run it longer than mixing it with "regular oil."


From here: https://mobiloil.com/en/faq/ask-our...ith-conventional-oil-cause-a-gel-to-form

 

[OVERKILL]

Originally Posted by ToadU
We are both arguing over different points. It may affect unique propriatry properties of a said oil however it won't damage the engine. All oils are compatible. Would I go around like a mad scientist mixing oils for the heck of it....no. Would it hurt to add a quart of brand X meeting spec to brand Y in the event you are low...nope. Not at all. There is no evidence I have ever seen to substantiate that. No evidence switching back and forth from Dino to Syn and back again is harmful ect. Dino and Syn are compatible as well.


My point, which I'd thought I'd made clear, is that a lubricant carrying a given approval when mixed with another product, is no longer qualified for that approval. You seem to have ceded that point with your "it may affect unique proprietary properties of said oil", which is exactly the issue. Oils are complex blends, altering; perverting that blend with something else makes the final product an untested wildcard. That doesn't mean it is going to cause engine failure or turn into axle grease, but it does mean that you've produced something likely inferior to what you had in the beginning. Typically, as I already noted, the performance most impacted is that of cold temperature, which is something you are not going to have an issue with in Florida.

 

[Shannow]

The miscibility standard requires that the oil be mixed with 8 reference oils, cooled to establish the new (not original) gel point. Heated to 150C, frozen to the gell point established in the first test, and then thawed.

to pass, the oil has to not drop out precipitates, nor split like salad dressing.

That it...that's ALL the compatibility standard offers....not that two 0W oils make a 0W oil, not that two SN oils when mixed would pass the standards for SN.

The compatibility test provides reasonable certainty that the major effects that they are looking for (precipitates or splitting) won't happen when the many thousands of oils on the street are mixed with any of the other thousands of oils on the street.

As to the EXTREMELY RARE occasions when it happens, I've linked the SAE papers before...in one case, the first service oil reacted badly with the factory fill in a fleet of cars. The subsequent mix gelled at temperatures above the starting temperature of the vehicles, and the engines failed due to air binding (failure to draw oil up the oil suction line).

Now both these oils passed the ASTM test and reference oils for compatibility, but the failure was in the interaction between PPDs, VIIs, and waxy elements of the oil. Not the splits or blows chunks aspects of the testing.

It's rare, but it can and does happen...and the SAE HAS investigated it.

So if you NEED a 0W oil...don't mix two 0W oils

 

[bbhero]

^^^^^^

I agree.

No need to temp fate at very, very cold temperatures. Like one could see in upstate NY, Vermont, NH, Maine, Minnesota, ND, SD, WI, Montana, Wyoming, Alaska etc...

I think in warmer places it obviously is no where near as much an issue.

 

[PeterPolyol]

Pfff you guys know nothing about genetics. It goes "boy, girl, boy, girl"