mixing Aeroshell 15w50 into Phillips 20w50?

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alanbreck

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AlanB
Engine oil mixing question,
I run Phillips XC 20w50 in my engine (IO-540). I have a few Aeroshell 15w50 qts left from elsewhere.
Is there any issue with using the occasional Aeroshell quart to top of the oil level? Or even running half and half?
 
Aeroshell says as long as all the oils approved for your aircraft, you can mix them however you like.
 
You'll get answers ranging from; it won't matter, to your engine will grenade in minutes. I vote for the first answer.
 
All aviation oils are mixable. That's part of the mil-spec. Mixing 15/50 and 20/50 will give you very predictable results, so I don't see why you wouldn't use whatever you have.
 
Hasn’t seemed to bother my airplane, sometimes you have to use what’s available .
 
alanbreck said:
Engine oil mixing question,
I run Phillips XC 20w50 in my engine (IO-540). I have a few Aeroshell 15w50 qts left from elsewhere.
Is there any issue with using the occasional Aeroshell quart to top of the oil level? Or even running half and half?
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I've mixed both in my pair of IO-540s. No issue.
 
kyleb said:
All aviation oils are mixable. That's part of the mil-spec.
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The mil-spec and/or SAE standards are what I would go by. I'm not terribly interested in what a specific oil manufacturer has to say, other than if it meets the standards or not. They say it must be ok to mix so I don't see a reason to get concerned.
 
kyleb said:
All aviation oils are mixable. That's part of the mil-spec. Mixing 15/50 and 20/50 will give you very predictable results, so I don't see why you wouldn't use whatever you have.
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they are mixable. But IIRC multivis oils aren't covered by the mil,spec, so that's kind of not the reason!
 
PaulMillner said:
they are mixable. But IIRC multivis oils aren't covered by the mil,spec, so that's kind of not the reason!
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You remember wrong, or you're looking at the wrong MILSPEC. MIL-L-22851D (the spec for AD aviation piston engine oil) most certainly handles multiweight oils. MIL-L-6082E which handles the non-AD oil only handles single weights.
 
This all reminds me of a story a friend of mine told me about when he was working at a Mercedes dealership with an old experienced mechanic. Story goes that they ran out of one oil and had to finish up with another. When asked if those oils could be mixed, the old mechanic put some on his fingers, rubbed it around and declared, they're both slippery.

Now on with the discussion.
 
That's one thing my old crusty CFI taught me during primary, all approved aviation piston oils are mixable.
 
...But smelled like a sandwich.
 
Margy has an "Endless Pool" which uses a 5HP Hydraulic pump to run a hydraulic motor inside the pool to generate the swim current. The hydraulic fluid? Not 5056 but canola oil. It's non toxic in case we get a leak I guess.
 
I remember back when I was renting. It seemed like the rental planes always needed the oil to be topped off after a long cross country. I just added whatever aviation oil was available at the FBO. I don't remember any time when I rented a plane that the specific brand of oil to use was specified on the aircraft.
 
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