The ole mixing oil question.....

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Jun 22, 2008
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I have a gallon of Rotella T4 15w40 and I have a 5qt jug of Pennzoil Euro-L 5w30.

Times are tight and I need to change the oil in my Eco-Diesel, but I have these two oils on my garage shelf.

Is there any issue mixing 4qts of T4 with 5qts of Euro-L?


............
 
I wouldn't, they're of drastically different formulations and while they should be miscible there's no guarantee that either really meets any of the listed certifications anymore and I probably wouldn't run it for a full OCI.
 
How many hours are you willing to spend researching the issue of mixing two vastly different oil formulations.....

Zero... that's why I am posting here..... Do you have any wisdom or level of scientific input?

Is anyone aware of lab tested blending???? Positives or negatives... please reference your studies.

.....
 
Zero... that's why I am posting here..... Do you have any wisdom or level of scientific input?

Is anyone aware of lab tested blending???? Positives or negatives... please reference your studies.

.....

I paid for an oil analysis of a blend.

They were the same brand and formula, 10w30 and 15w40 50/50 ratio. The final viscosity was as predicted by the Widman calculator. I always got good used oil analysis with this blend.
 
Both are diesel oils.
Having never owned a diesel I don't even have leaning except to think if the two products were "modern enough" -and I believe they are- I'd probably mix em.
 
For the 825th time.

As long as the mixed oils have an API license or have otherwise passed ASTM D6922 then they are miscible.

Which doesn’t mean they still retain any license, certification or approval the individual oils may have originally held. Nor necessarily meet the requirements for any particular winter rating.

But it does mean there won't be an "issue" nor harm your engine.
 
Is anyone aware of lab tested blending???? Positives or negatives... please reference your studies.
ASTM D6922-13(2018)

Standard Test Method for Determination of Homogeneity and Miscibility in Automotive Engine Oils

Significance and Use


5.1 It is important that engine oils from different manufacturers be homogeneous and miscible with each other, because operators of automotive engines often do not have prior knowledge of the manufacturer of the oil that is currently used in their application, and engine failure can occur if oils are combined that do not stay homogeneous and function properly.
 
For the 825th time.

As long as the mixed oils have an API license or have otherwise passed ASTM D6922 then they are miscible.

Which doesn’t mean they still retain any license, certification or approval the individual oils may have originally held. Nor necessarily meet the requirements for any particular winter rating.

But it does mean there won't be an "issue" nor harm your engine.
Exactly. The odds that something is going to be negatively impacted in the formulation are pretty high, but it's not going to cause any problems unless you are geographically situated where testing the integrity of the Winter rating is liable to happen, as the Winter rating is the most likely casualty.
 
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