They prefer it over AS15W50, and definetely over Total 15W50.
It would be interesting what data they base this on.
Firstly because Total is reportedly Shell but with a different name on the bottle.
Secondly because it is really hard to tell the difference between any oil and any other oil if the engine is operated regularly. I have never seen any significant difference in oil analysis between base oil types. The only one I did see was with Camguard which greatly reduced the wear of the hard metals. And if the engine is allowed to corrode then you will get so much crap in the oil that it will be hard to reach conclusions.
That could be because Aeroshell have a commitment for a constant composition formula, while Total may make it vary if compounds / additive are missing, replacing them “on the fly”.
As I am here 
…
Are you attached, @Peter, to the Lycoming additive (LW-16702) ?
Or would you skip it if you have Camguard ?
I have forgotten what it is…
It is embedded in AS15W50 and in straight AS W*+*
There is only one Lycoming engine type which requires it.
Phillips doesn’t have it.
But I am sure you know all that !
I moved from synthetic AS 15W50 to Philips X/C 20W50 with Camguard. I do not add Lycoming LW-16702 which is only required for the C172N engine. It’s a friction modifier.
I had 2 stuck valves after 10 years of AS 15W50 and I observed deposits in the engine under the valve covers. The valve guides had the same stuff in them. After switching to the mineral oil, I no longer observe the deposits and the valve guides still look clean (I remove the valves every year to have a look). I would not use 15W50 again.
The reason I use X/C 20W50 instead of a mono grade mineral oil is that I like the flexibility of not having to schedule my oil changes based on ambient temperatures.
achimha wrote:
After switching to the mineral oil, I no longer observe the deposits and the valve guides still look clean (I remove the valves every year to have a look). I would not use 15W50 again.
I know only one owner/pilot in my area who who uses anything than mineral oil (typically straight grade AS) and I’ve never heard of anybody local having issues with deposits, stuck valves etc. Maybe there really is a correlation.
achimha wrote:
After switching to the mineral oil, I no longer observe the deposits and the valve guides still look clean
This seems to corroborate Mike Busch’s claim that synthetic oils do not maintain particulates in suspension and they therefore form some sludge.
My approach towards Phillips oil was also lead by Achim strategy and past experience, he shared with me during the winter.
Now my AS stock has gone, I am quite inclined to do this way.
Arguments (or opinions) are pretty numerous.
Here is Cessna piston support answer, to the oil recommendation question:
Textron aviation does not have a specific oil manufacturer of oil that we recommend be used in the airplane engines. For the 182T the oil must conform to SAE J1899 for ashless dispersant oil. 20W50 is called out in the service manual as a good overall viscosity for engine operation. When the airplanes leave the factory they are filled with straight mineral oil for the break in period that meets SAE J1699.
