Ask Cheri

What’s the difference between FECO and RSO? 

By Cheri Sicard
June 7, 2023

Dear Cheri,

Are FECO (full extract cannabis oil) and RSO (Rick Simpson oil AKA Phoenix Tears) the same thing?  If not, what is the difference?

While both FECO and RSO are powerful cannabis concentrates, they are not exactly the same but they are similar.

FECO is kind of a broad term and there are different methods for making FECO.  RSO is a type of FECO but FECO is not necessarily RSO. 

These two items function similarly and many people use the terms interchangeably.  So if you are looking for the healing property of FECO or RSO they can pretty much be used interchangeably. 

However, when Rick Simpson first made his cancer curing oil he used naphtha as a solvent.  This is also the method outlined int he full length documentary about Simpson, Run From the Cure (watch it for free on YouTube at this link). 

Simpson still touts the use of denatured alcohols, but I have yet to hear a compelling reason why.  These have chemical additives, some of which are carcinogenic.

Years ago I discussed this with Dr. Jeffrey Raber who said it was a terrible idea!  It made sense to him whatsoever, especially when you can use a safer, food grade solvent.

Now in theory, all the solvent should be gone by the time you use the concentrate.  However, after testing 1000s of samples from Souther California dispensaries, Dr. Raber found this was not always the case.

Why take a chance? Use a food grade solvent whenever making FECO and never worry.  That's my philosophy.

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About the author

Cheri Sicard is the author of Mary Jane: The Complete Marijuana Handbook for Women, and The Easy Cannabis Cookbook.  Her online courses at have educated 1000s of students about marijuana, cannabis cooking for home cooks, and making infused topicals.

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