[AX-O]

In my previous airplane I used Aeroshell 15W-50. So I have a case in my hangar. The previous owner of my RV-4 was using 100 plus SAE 50. Would it be acceptable to add the Aeroshell 15W-50 to the current oil? Or do I need to go buy more 100 plus SAE 50 and use that until the next oil change? Thanks for any advice you can provide.

http://www.shell.com/home/content/aviation/products/lubricants/piston_engine_oils/w15w50/

http://www.shell.com/home/content/aviation/products/lubricants/piston_engine_oils/w100plus_w80plus/

 

[Mel]

Yes, any oils meeting the aircraft specifications can be safely mixed.

 

[Doug]

I am not sure I understand exactly what you are asking but note that Shell (or perhaps it was Lycoming?) has specific instructions about switching from long term use of straight mineral (eg Aeroshell 100) to the ashless dispersant oils (Aeroshell W100) that includes a mandatory oil change after 5 hours.
This is to do with flushing out the sludge and clogging filters and passageways.
Dig around for the data, sorry I cannot remember where I read this.
Doug

 

[aerhed]

Pour it in. W100 plus has the same antiwear additive as 15W-50 and is not a "straight mineral". It is an AD, so life goes on.