08/24/2026
A long but good read.🌱
What is RSO? What is FECO? What’s the difference?
Author’s Note: FECO versus RSO isn't really one comparison. It's dozens of possible extractions hiding behind two names… especially here in Oklahoma.
RSO
RSO stands for Rick Simpson Oil. It originated with Canadian cannabis activist Rick Simpson in 2003.
After being diagnosed with cancer himself, Simpson began making a highly concentrated, full-spectrum extract he called Phoenix Tears. Made using light aliphatic naphtha as the solvent, the final concentrate was used topically/externally on his own skin cancer.
In 2008 his documentary Run From The Cure was released and detailed the medicine’s origin story. Soon after, he would release written instructions for others on how to make the medicine.
Simpson later became known for promoting high-dose RSO protocols for serious illness, particularly cancer. Those treatment claims have not been established in controlled human clinical trials, though patient-reported accounts of remission and benefit have continued to circulate extensively throughout the medical cannabis community for more than two decades.
His work nevertheless played THE pivotal role in popularizing whole-plant cannabis extracts within the modern medical cannabis movement.
In 2023 Rick Simpson released an interview where he said, “There are many people out there selling oil and using my name, or they’re putting out oil and calling it RSO, but it’s not RSO.”
Simpson’s original solvent of choice was light aliphatic naphtha, although he later discussed 99% isopropyl alcohol as an alternative. Neither choice maps neatly onto what Oklahoma consumers encounter today.
Modern regulated extraction operates under very different processing, testing and residual-solvent standards. Naphtha does not fit neatly within Oklahoma’s modern regulated extraction framework and is not among the solvents for which current OMMA rules establish a residual-solvent threshold, which is part of why the term “RSO” has become increasingly disconnected from Simpson’s original process.
Here in Oklahoma, RSO has a few different meanings that we will explore more deeply below when we take a look at the Oklahoma market offerings.
FECO
FECO (pronounced “Fee-co”) stands for Full Extract Cannabis Oil.
Unlike RSO, which refers historically to its creator and his particular methodology, FECO describes the extract itself: a concentrated cannabis oil intended to retain a broad spectrum of the compounds extracted from the plant.
FECO does not appear to have a single documented inventor or moment of creation. In many ways, the extraction philosophy behind it is much older than the name itself. Alcohol-based cannabis extracts and tinctures were used medicinally more than a century before either FECO or RSO entered our modern cannabis vocabulary.
By 2013, the term Full Extract Cannabis Oil was in documented use within the medical cannabis movement. An issue of O’Shaughnessy’s described “WAMM’s Full Extract Cannabis Oil,” produced using Everclear as the solvent and concentrated into an oil.
WAMM, the Wo/Men’s Alliance for Medical Ma*****na, was founded in 1993 by Valerie and Michael Corral in Santa Cruz. WAMM became one of the most historically important medical-cannabis collectives in the United States, particularly because of its work with seriously and terminally ill patients. Valerie Corral later helped develop California’s Proposition 215, passed in 1996 as the first state medical-cannabis law of its kind.
But similar to RSO, there is no universally agreed-upon or enforced scientific or pharmacopoeial definition of FECO.
That means here in Oklahoma, not all FECOs are made the same.
And just like RSO, we’ll dive a bit more into that below.
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So What Actually Makes One RSO or FECO Different From Another?
This is where the conversation gets considerably more complicated.
Two syringes can both say “RSO.” Two others can both say “FECO.” All four can contain completely different extracts.
That’s because the final oil is shaped by far more than the name placed on the package.
The solvent matters.
The temperature of that solvent matters.
The temperature and condition of the cannabis going into it matter.
How long the extraction runs matters.
And what happens to the extract afterward matters.
Change any one of those variables and you begin changing which compounds make it out of the plant and into the final oil.
Change several of them at once, and two products carrying the exact same name can become very different medicines.
Before we start comparing what Oklahoma processors are calling RSO and FECO, we need to understand something important:
The name on the package doesn’t make the extract.
The process does.
There are several major variables that determine what ultimately makes it out of the flower and into that syringe.
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The Solvent
Cannabis can be extracted using ethanol, isopropyl alcohol, hydrocarbons such as butane or propane, CO₂, water and several other methods.
Each solvent has different chemical properties and therefore different selectivity. In simple terms, different solvents are better at dissolving different compounds.
Ethanol is particularly interesting because it can extract cannabinoids and terpenes, but because of its polarity it can also pull chlorophyll, sugars and other more polar compounds from the plant depending on temperature, time and handling.
When ethanol is brought to very low temperatures, its extraction becomes more selective by reducing the solubility and co-extraction of many unwanted plant compounds while cannabinoids remain readily extractable.
Isopropyl alcohol is a broad-spectrum solvent capable of extracting a wide range of cannabis constituents. It doesn’t just pull cannabinoids efficiently. Depending on temperature and contact time, it can bring a much wider swath of the plant along with them, including pigments, fats, waxes and other compounds.
Hydrocarbons such as butane and propane behave differently because they are predominantly nonpolar solvents. They are extremely effective at extracting cannabinoids and terpenes while generally bringing along much less chlorophyll than alcohol-based extraction. They can still co-extract waxes and lipids, which is why hydrocarbon extracts may undergo dewaxing or other refinement afterward.
CO₂ adds another layer entirely. Supercritical CO₂ extraction can be manipulated through pressure, temperature and, in some systems, co-solvents to change what the process preferentially extracts.
So even “CO₂ extracted” does not describe one universally identical extract.
Before we even talk about whether something is “RSO” or “FECO,” simply changing the solvent can create a fundamentally different extract.
At Bee Elevated, we extract using ethanol.
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The Temperature of the Solvent
This is one of the biggest variables in ethanol extraction.
Ethanol can be used warm, at room temperature, cold or extremely cold.
As ethanol gets colder, its extraction becomes more selective. Cannabinoids remain readily extractable while many unwanted compounds such as chlorophyll and waxes become less soluble. Warmer ethanol generally extracts a broader range of plant material along with the cannabinoids.
A warm ethanol extract may literally contain more of the plant, but an ultra-cold ethanol extract may contain a greater proportion of the compounds we were actually trying to extract in the first place.
But that distinction is important:
More selective does not automatically mean therapeutically superior, and broader extraction does not automatically mean worse.
Selectivity is a design decision.
The important question is whether the process preferentially captures the compounds you want while minimizing the compounds you don't.
Several Oklahoma products currently sold as “RSO” are produced using warm-to-hot ethanol extraction.
At Bee Elevated, we chill our ethanol to -65°F before extraction. By using ultra-cold ethanol, we intentionally limit how much chlorophyll, wax and other unwanted plant material comes along for the ride.
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The Temperature of the Flower
The solvent isn't the only thing that can be cold.
Processors may extract room-temperature flower with cold solvent, cold flower with room-temperature solvent, both cold, or both at room temperature.
And those combinations are not interchangeable.
Temperature affects how readily different compounds move from the plant matrix into the solvent. Keeping the plant material cold also helps maintain the low-temperature environment throughout extraction rather than immediately warming your carefully chilled solvent when the two meet.
There is an enormous difference between flower that has spent months improperly stored in uncontrolled heat and flower that has been properly stored and prepared for extraction.
At Bee Elevated, we bring our flower down to the same -65°F before extraction to ensure that it is at the same temperature as the solvent when they meet.
The important number isn’t just solvent temperature.
It’s slurry temperature, meaning the temperature of the solvent and biomass once the two are combined.
If ultra-cold ethanol hits room-temperature flower, the biomass immediately transfers heat into the solvent and changes the conditions under which extraction is occurring. Starting with both the solvent and flower cold minimizes that temperature swing and keeps the extraction operating closer to its intended conditions.
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Contact Time and Agitation
Then there is the question of how aggressively and how long the solvent interacts with the flower.
Some extraction methods use long soaks. Others rely on much shorter contact periods. Some continuously agitate the material while others use relatively little movement.
Generally, longer contact and greater extraction intensity give the solvent more opportunity to dissolve compounds from the plant.
That can increase extraction yield, but it can also increase the amount of material you never wanted in the finished oil.
More is not always better.
Research on cold ethanol extraction demonstrates that extraction time, temperature and the solvent-to-biomass relationship all influence the resulting extract.
At Bee Elevated, we do it on purpose. Our goal is selective extraction rather than prolonged soaking.
We want the ethanol to efficiently capture the compounds we're targeting without unnecessarily extracting the rest of the plant along with them.
This means that not every extraction is the same, even if they all begin from the same place.
Cold and smooth.
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Filtration and Refinement
Once the cannabinoids are in solution, the process still isn't finished.
An extract may simply be mechanically filtered, or it may undergo additional filtration, winterization or other refinement intended to remove waxes, lipids, chlorophyll or suspended plant material.
This creates an interesting paradox when discussing the word “full.”
Full does not mean everything.
No extraction process captures every molecule that existed in the original flower in exactly the same proportions. Every solvent selects. Every temperature selects. Every filtration or refinement decision selects again.
In practical terms, “full spectrum” is better understood as an attempt to preserve meaningful chemical breadth rather than a claim that the finished syringe is a perfect molecular duplicate of the original plant.
Extracts produced using warm or hot solvent that undergo little additional refinement can contain substantially more lipids, waxes, chlorophyll and other co-extracted plant material.
More refinement can produce a cleaner extract, but every additional purification step also has the potential to change its chemical composition.
Cold ethanol can reduce the extraction of waxes and chlorophyll in the first place, which can decrease the amount of downstream cleanup required.
At Bee Elevated, we address the problem before and during extraction to avoid unnecessary post-processing steps that alter the concentrate.
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Decarboxylation
Cannabis naturally produces most of its major cannabinoids in their acidic forms: THCA, CBDA, CBGA and others.
Over time, and particularly when exposed to heat, those acidic cannabinoids lose a carboxyl group and convert into their neutral forms, including THC, CBD and CBG, through a process called decarboxylation.
Some producers decarboxylate the flower before extraction. Others extract predominantly acidic cannabinoids first and decarboxylate the resulting oil later. Processing itself can also introduce heat.
Where and how decarboxylation occurs matters because heat doesn't affect cannabinoids alone. Volatile compounds, particularly terpenes, can also be lost or altered during processing.
Many industry-standard practices expose extracts to significant combinations of time and temperature. Some of this comes from outdated industry information, while some comes from a sad industry reality where sometimes the goal is faster, not better.
At Bee Elevated, we treat decarboxylation as its own controlled stage of production, rather than simply using a hot extraction and allowing extraction and decarboxylation to blur together.
Through years of our own process development, Bee Elevated settled on a low-and-slow decarboxylation protocol of 150°F for 72 hours, designed to achieve decarboxylation while minimizing unnecessary thermal exposure and preserving as much of the extract's original chemistry as possible.
That wasn't chosen theoretically. It came from iterative process development and analytical testing to maximize both cannabinoid and terpene retention.
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Solvent Removal and Finishing
Finally, the solvent has to leave.
Historically, this could mean relatively crude evaporation over heat.
Modern commercial processing can use controlled evaporation under reduced pressure, allowing solvent recovery at lower temperatures.
That distinction matters because the goal isn't simply:
“Get the alcohol out.”
The amount of heat, vacuum and time the extract experiences during finishing can continue changing the chemistry of the oil even after extraction itself has ended.
Commercial pressure naturally rewards throughput, which can encourage hotter and faster solvent recovery. But increasing temperature to shorten processing time also increases the thermal burden placed on the extract.
At Bee Elevated, we complete our final purge at the lowest effective temperature our process allows, generally between 105–120°F with the least amount of time necessary for a full purge.
And none of these variables exists in isolation.
Cold solvent with warm flower is different from cold solvent with frozen flower.
A long cold soak is different from a short cold wash.
Warm extraction followed by aggressive refinement is different from warm extraction left largely untouched.
Every variable interacts with the others.
So even when somebody tells you their product is “ethanol extracted,” we still don't know nearly enough to understand what is actually in the syringe.
We need to know:
Which ethanol extraction?
Warm solvent or cold?
Warm flower or frozen?
Long soak or short contact?
Highly refined or minimally refined?
Decarbed before extraction or afterward?
High-heat solvent removal or controlled recovery?
And suddenly our original question…
“What's the difference between RSO and FECO?”
…doesn't have a two-column answer anymore.
There is no neutral extraction process. Every extraction is a series of choices about what to bring forward, what to leave behind and what to change afterward.
It has a matrix.
Starting point
Extraction environment
General tendency
Ultra-cold ethanol + ultra-cold flower
Low slurry temperature
More selective extraction, reduced chlorophyll/wax co-extraction
Ultra-cold ethanol + warm flower
Slurry warms on contact
Some of the intended cold selectivity can be lost
Warm ethanol + cold flower
Slurry warms
Broader ethanol extraction as equilibrium shifts
Warm ethanol + warm flower
Warm slurry
Greater co-extraction of pigments, waxes, lipids and other plant constituents
Isopropanol + biomass
Broad solvent extraction
Cannabinoids plus potentially broad co-extraction depending on temperature/time
Hydrocarbon + flower/live material
Predominantly nonpolar extraction
Strong cannabinoid/terpene recovery with relatively low chlorophyll extraction
CO₂
Pressure/temperature-dependent
Highly tunable extraction profile
These aren't recipes or guarantees. They're tendencies. Change contact time, agitation, solvent ratio, biomass condition, refinement or finishing, and the outcome changes again.
And now we're ready to talk about Oklahoma.
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Oklahoma
Market Note: Products and processing methods change. The examples below reflect products and publicly available information in the Oklahoma market as of August 2026.
One of the big issues in Oklahoma is transparency.
And I want to make one thing very clear before we go any further:
This isn't an argument that BHO is bad, CO₂ is bad, rosin is automatically better, ethanol is automatically superior or distillate doesn't have a place.
They are different extraction and refinement technologies capable of making very different products.
My problem is when those differences disappear behind terminology that leads a patient to believe they're buying one type of extract when they're actually buying another.
In some ways, the term RSO has become a dumping ground here in Oklahoma.
It can mean the extraction was done with warm flower and hot ethanol. Compared with properly controlled cold ethanol extraction, warmer ethanol can co-extract substantially more chlorophyll, lipids, waxes and other plant constituents along with the cannabinoids.
It can also mean that you got something made with isopropyl alcohol. Isopropyl alcohol has historically been used to make RSO. Oklahoma-hosted cannabis manufacturing guidance has specifically described isopropanol as “not recommended.” Current OMMA rules nevertheless anticipate its possible use by requiring finished products to contain less than 1,000 ppm residual isopropyl alcohol.
It can mean you got last year’s BHO (butane hash oil) melted back down. It might have gotten run back through ethanol. It might have gotten a couple more rounds of CRC (color-remediation filtration). It might have just gotten melted back down and sucked up in a syringe.
Patients and consumers often flock to these brands as they are
able to be sold cheaper and have a lighter coloration.
Lighter does not always mean better when it comes to full-spectrum extracts.
I will give credit to the companies that clearly explain that they are doing this.
For example Sooner Glue’s Live Resin RSO.
It’s live resin, in a syringe.
There are SOME companies, like Mint, that use the terminology as a marketing term not an extraction definition. In all reality, Mint makes FECO.
On the flip side, companies like Rare Extracts lean heavily on the words RSO despite being a butane-derived extract who even markets their butane-RSO as dabbable.
In at least one case with a different company, even the batch naming associated with an RSO product included “BHO28G,” illustrating just how disconnected the retail term can become from the underlying extraction process.
Perhaps the most extreme contradiction we’ve come across recently was a company selling an RSO while publicly describing its oil as undergoing SIX rounds of distillation.
But what bothers me most is when extraction methods are obscured, misrepresented or described in ways that don’t match the process used to make the product.
On the other side of the coin, ethanol appears to be the dominant extraction method among Oklahoma products marketed as FECO whose processes are publicly identifiable.
The distinction here typically comes down to time, temperature, agitation and post-processing.
The primary exception being AeroLabs with their CO₂-extracted FECO.
Other notable exceptions are Tribe’s Fully Activated Hash Rosin Oil (FAHRO) and Native Veteran’s Solventless RSO made for Veterans.
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So How Do You Actually Tell The Difference
This entire post would be pretty useless if I spent all this time telling you how complicated RSO and FECO are without giving you a way to make better decisions for yourself.
So here’s the biggest takeaway:
Stop asking only, “Is this RSO or FECO?”
Start asking:
“How was this made?”
Because those three letters on the package may tell you surprisingly little about what is actually inside the syringe.
Here are the questions I would ask.
1. WHAT SOLVENT WAS USED?
Ethanol?
Isopropyl alcohol?
Butane or propane?
CO₂?
No solvent at all?
That answer alone tells you considerably more than “RSO” or “FECO.”
If the answer is “solventless,” ask what that means. Is it activated hash rosin? Rosin with something added back afterward? Something else entirely?
Specificity matters.
2. WAS THE EXTRACTION HOT OR COLD?
Especially with ethanol, this matters tremendously.
“Ethanol extracted” is not enough information.
Was the ethanol room temperature?
Chilled?
Ultra-cold?
Was the flower cold too?
Remember:
The solvent temperature and the slurry temperature are not necessarily the same thing.
Cold ethanol hitting warm biomass is a different extraction environment than cold ethanol hitting equally cold biomass.
3. WHAT MATERIAL WENT INTO IT?
Was it fresh frozen flower?
Properly stored cured flower?
Trim?
Shake?
Old biomass?
A blend of multiple strains?
The quality of an extraction can never completely outrun the quality of the material being extracted.
Extraction is selection, not creation.
A processor can preserve, concentrate, remove, transform or lose compounds that were present in the starting material, but the extractor cannot magically recover a chemical profile that wasn't there to begin with.
A great extraction process does not magically turn bad starting material into great medicine.
And fresh frozen isn't automatically ‘better’ than properly cured flower either. They are different starting materials suited to different extraction goals. For something like live resin, preserving freshly harvested material is part of the entire objective. For another extract, properly dried and cured material may be exactly what the processor wants.
What matters is the quality and condition of the material, how it was stored and whether it fits the process being used.
4. WHAT HAPPENED AFTER EXTRACTION?
This one gets overlooked constantly.
Was it winterized?
Filtered?
Decarboxylated?
Distilled?
Was anything removed?
Were cannabinoids or terpenes added back afterward?
Was the extract blended with distillate?
Was it formulated after extraction?
Two products can begin with exactly the same flower and solvent and still finish as dramatically different products depending on what happens next.
5. LOOK AT THE COA, BUT KNOW WHAT IT CAN AND CANNOT TELL YOU
A Certificate of Analysis can tell you a lot.
Look at the cannabinoid profile.
Not just THC.
Are minor cannabinoids present?
Look at the terpene profile if it was tested.
Look at residual solvents and contaminants.
Look at the total cannabinoid concentration.
But understand this:
A COA is a chemical snapshot of the finished product. It is not a complete history of how that product was made.
A passing residual-solvent panel does not necessarily tell you which solvent was used during extraction. It tells you which tested residual solvents were detected in the finished product and whether those residues fell within applicable limits.
“Purged successfully” and “never used” are not the same statement.
6. BE CAREFUL USING COLOR AS YOUR GUIDE
RSO is often associated with being almost black or dark green.
FECO can range dramatically in color, from amber and brown through green and nearly black depending on the material and process.
But color by itself tells you very little.
A dark color does not automatically mean “more full spectrum.”, it may contain more chlorophyll, oxidized compounds or other co-extracted plant material.
A lighter color does not automatically mean “more refined.”
And a high THC percentage absolutely does not automatically mean “better medicine.”
You cannot determine which simply by holding the syringe up to the light.
Dark does not automatically mean full spectrum.
Light does not automatically mean stripped.
Ask how it was made.
7. DON'T LET POTENCY BECOME THE WHOLE CONVERSATION
If one syringe tests at 65% THC and another tests at 85%, that does not automatically make the 85% product superior.
If our only goal were THC concentration, we already have technologies specifically designed to isolate and concentrate THC.
The entire reason people became interested in whole-plant extracts in the first place was that cannabis contains considerably more than THC.
Look at the whole chemical profile.
Not just the biggest number on the label.
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The Final Rub
What consumers should understand is that:
RSO is not one thing.
FECO is not one thing.
And neither acronym tells you whether an extract is good, bad, clean, dirty, selective, crude, refined, solventless, hydrocarbon-derived, ethanol-derived or anything else without additional information.
So rather than asking:
“Which is better, RSO or FECO?”
Ask:
What went into it?
What pulled it out?
At what temperature?
What was removed afterward?
What was added afterward?
And what does the finished chemistry actually look like?
Those questions will teach you more about the medicine than the three or four letters printed on the front of the package ever could.
Ask better questions.
Reward the processors willing to answer them.
Because ultimately...
The name on the syringe is marketing.
The process is chemistry.
And an educated patient should have access to both.
What a crazy journey for three to four little letters.
In our next post we will discuss all the different usages and benefits of medicating with RSO/FECO.
Bee the change, Bee Elevated
