Topping off with XPS in 912iS

For what it's worth:

XPS is a full synthetic oil

Aeroshell Sport Plus 4 is a semi synthetic oil.

Personally I would not combine them.

As for changing from Plus 4 to XPS -Cant see the point in a "flush" - I would do a usual oil/filter change, just use XPS in place of Plus 4 and then a second oil change, say 5-10 hrs later, again with XPS.

Rational -

Do not mix oils of diffrent chemical makeup.

Flush may remove most of the old Plus 4 oil however some flush will remain to contaminate new XPS

By doing an oi/filter change you will be removing almost all the Plus 4. The small amount that remains, will be highly diluted by the replacement XPS.

Interim oil/filter change at 5-10 hrs, using XPS, will further dilute the already small amount of Plus 4

Alternative: Drain all Plus 4 oil from system. Replace with XPS & do a full oil system purge. Future service intervals as per Rotax recommended.

Sean is correct. 

There is a procedure in the MML that works.  I would follow up with an additional oil change at 25 hours after to be sure all traces of the offending oil are gone.  

The XPS must be used for the type 916.  We have already heard about some engines with the Shell sliping the overload clutch on takeoff.  While it cant be sure that is the issue Rotax has advised any engines with slipping and the Sport Plus 4 in a 916 will not be covered.  

Cheers

Service Instruction for “Selection of suitable operating fluids for ROTAX® Engine Type 916 i (Series), 915 i (Series), 912 i (Series), 912 and 914 (Series)” dated 07 May 2024 does not contain procedures, nor contain any NOTES, CAUTIONS or WARNINGS regarding transitioning from AeroShell Sport Plus 4 to XPS lubricant.  Of note, both AeroShell Sport Plus 4 and XPS are authorized lubricants by Rotax.  

Accordingly, it’s my view the “OIL SPECIFICATION NOT RESPECTED” procedure contained in the current Maintenance Manual Line (MML) for Rotax Engine Type 912 i Series, Ref No.: MML-912 i | Part No.: 898743 … Effectivity: 912 i Series, Edition 2/Rev. 2, dated May 01/2023, is not required.  Also of note, the Rotax MML does not provide any procedures, nor any NOTES, CAUTIONS or WARNINGS about transitioning from AeroShell Sport Plus 4 to XPS lubricant.  

That said, it’s not unreasonable to conclude arbitrarily mixing AeroShell Sport Plus 4 and XPS could POSSIBLY create chemical compositions that MIGHT result in oil specifications not recognized by Rotax, albeit that possibility seems remote.  Why?  One would think Rotax would have provided instructions for how to transition from AeroShell Sport Plus 4 to XPS if there were any safety issues mixing the two in any combination. 

So for all these reasons, I believe there’s nothing wrong with Rotax Wizard’s conservative approach.  Nevertheless, I am currently using the logical and reasonable approach to transition from AeroShell Sport Plus 4 to XPS that Sean also offered on my own RV-12iS.

Respectfully submitted,

-Pat Ellis

Hi All

OK, did some calls and this is the response. 

Do not "top up" with XPS over Aeroshell.  They are different base oils.  The good part is you can simply do a complete oil change and filter, plus clean the oil tank, then replace it with XPS.  The small amount of residual in the lines and cooler are not an issue.  If you do flush the lines and cooler you have to start from square one with an oil purge and be sure you have to trapped air.  The XPS engineers do not feel the small amount left in doing a regular oil change and filter is enough to worry about.  

Hope that helps.

Cheers