The answer in 30 seconds
Classic has the cleaner evidence-led start for one territorial behaviour. Optimum is the broader hypothesis, not a proven universal upgrade.
Start the conversation with Classic for one defined behaviour such as unwanted scratching or urine spraying after medical and litter-box causes have been addressed.
Consider an Optimum trial when several stress-related signs occur together or the question is broader inter-cat tension — while separating resources and escape routes first.
Buy neither yet when the behaviour changed suddenly, the outcome cannot be counted, the outlet is obstructed, or the household will not reassess at day 30.
Amazon Associates + OneLink · FR, BE, US, CA, UK and IE configured. The destination is a selection page, not one guaranteed model. Check Classic or Optimum, starter kit or refill, plug type, seller, local price and returns.
Search results usually ask which box sounds more powerful. A useful comparison asks four harder questions: what exact formula was studied, through which delivery device, in which behaviour, and whether the household can prove that another refill is worth buying.
Search landscape · checked 1 September 2026
The missing angle is a falsifiable household test
Leading pages explain the range and name a winner. They rarely separate exact-formula evidence, recurring cost by airflow zone and a stopping rule.
Formula and delivery device get blurred
A positive study on Classic, a powered pheromone complex or an Optimum collar does not automatically prove the exact Optimum wall diffuser — or head-to-head superiority.
One refill price is not a household budget
Coverage depends on open zones, not only floor area. A closed floor plan can multiply the annual cost even when the home is under the advertised square-foot limit.
A winner badge has no stopping rule
Without a seven-day baseline, one observable outcome and a day-30 decision, normal variation can turn into an endless subscription by impression.
Exact claims, exact limits
FELIWAY Classic vs Optimum comparison
Both are 48 mL plug-in systems marketed for continuous 30-day use. The difference that matters is the question each trial is designed to answer.
| Decision point | Classic | Optimum | Why it matters |
|---|---|---|---|
| Brand position | A feline facial-pheromone analogue for territorial security | A newer pheromone complex marketed for a broader range of stress-related signs | Positioning is a trial hypothesis, not proof that one formula is universally stronger. |
| Typical starting question | One defined territorial behaviour, such as scratching or spraying after medical causes are excluded | Several stress-related signs or a broader household situation, including inter-cat tension | Choose one primary outcome even when several signs exist. |
| Most direct diffuser evidence | Large randomised placebo-controlled home trial for unwanted scratching; older small controlled spraying study | Initial home diffuser study was open-label and uncontrolled | The exact evidence base is not symmetrical. |
| Direct Classic-vs-Optimum diffuser trial | No independent direct trial found | No independent direct trial found | A search-result winner cannot be treated as a clinical ranking. |
| Published Optimum evidence | Not applicable | Positive randomised study exists for a prototype collar, not the plug-in diffuser | Delivery form matters; a collar result cannot be copied onto the diffuser. |
| Refill duration | 48 mL, marketed for up to 30 days | 48 mL, marketed for up to 30 days | Budget roughly one refill per active zone per month. |
| Stated coverage | Up to 700 sq ft for one open area | Up to 700 sq ft for one open area | Closed doors, separate floors and disconnected rooms can create more than one zone. |
| Use pattern | Plugged in continuously, 24/7 | Plugged in continuously, 24/7 | Switching off overnight makes the trial harder to interpret. |
| Diffuser head | Manufacturer says replace after six months | Manufacturer says replace after six months | A realistic annual budget includes the hardware cycle, not only twelve liquids. |
| Placement | Open outlet in the cat's main room; clear space above | Open outlet in the cat's main room; clear space above | Behind furniture, curtains or doors is not a valid test position. |
Official US product pages and FAQ accessed 1 September 2026. Coverage and price references are manufacturer claims, not guarantees for a particular home.
Evidence ladder, not star rating
What the studies can — and cannot — prove
Evidence quality changes when the comparator, delivery device or setting changes. That is why four positive headlines do not make one direct product ranking.
Large controlled home trial
In 1,060 cat–owner pairs, 83.5% of the pheromone group and 68.5% of the placebo group improved in scratching frequency by day 28. The difference supports an effect, while the large placebo response warns against judging by memory alone.
Funded by Ceva; several authors declared company relationships.Small double-blind signal
A double-blind placebo-controlled trial included 22 cats with urine spraying. It is relevant but small and older, so it should not carry the same weight as a modern large trial.
Useful supporting evidence, not a guarantee for every cause of house-soiling.Real homes, weak causal design
The first published Optimum diffuser study reported improvements across several behaviours in home settings, but it was open-label and had no placebo control. Expectation and changes made at home cannot be separated cleanly.
This is the exact delivery format, but not the strongest design.Controlled result, different device
A randomised placebo-controlled study found improvement in three of four assessed behaviours using a prototype collar with the new complex. That supports biological plausibility, not proof that the plug-in diffuser beats Classic.
Do not convert a collar result into a diffuser head-to-head claim.Interactive trial and annual-cost planner
Count zones before you compare refill prices
Default prices reflect the official US reference prices seen on 1 September 2026. Replace them with the live prices after redirection; this calculator is a planning model, not an offer.
The prerequisite no diffuser can replace
Build security into the room before adding a signal
The Feline Veterinary Medical Association's environmental guidance centres safe places, separated key resources, scratching and play opportunities, predictable positive interaction and respect for the cat's sense of smell.
Hide and observe
Provide enclosed and elevated choices so the cat can control distance instead of being trapped in the conflict zone.
Separate, do not cluster
Food, water, litter and rest are less useful when one cat can block the only route to all of them.
Scratch, hunt and play
Redirect scratching to stable surfaces and create predictable play rather than treating normal needs as pathology.
Map tension, not only fights
Staring, blocking, chasing, displacement and chronic hiding can matter before overt injury appears.
Installation audit
A blocked diffuser is not a fair product test
FELIWAY's FAQ states one diffuser for an open area up to 700 sq ft, continuous use, about 4 ft of clear space above and head replacement after six months.
Use the cat's real activity zone
Choose the room where the target behaviour happens or where the cat spends the most time, not the most convenient hidden outlet.
Keep the plume unobstructed
The manufacturer calls for about 4 ft (1.2 m) of clear space above the diffuser. Heat and vapour should not meet a shelf, curtain or cabinet.
Hide it behind furniture
A blocked outlet compromises dispersion and turns a placement failure into a false product verdict.
Use adapters or extension leads
The official FAQ says to use the local-voltage wall outlet directly, not a multi-plug, adapter or extension cord.
37 days from baseline to verdict
The 30-day protocol that prevents wishful thinking
The treatment window is 30 days; the seven days before it create the baseline. Keep the outcome and the room stable enough to interpret.
- 01Days −7 to −1
Record a baseline
Choose one primary behaviour. Count events, locations or conflict episodes at the same time each day. Note visitors, building work and routine changes.
- 02Day 0
Fix the test environment
Place the diffuser in the active zone, keep clear space above it and correct obvious resource problems. Photograph the setup so placement does not drift.
- 03Days 1–7
Observe without chasing noise
Keep the unit on 24/7 and avoid changing five other things at once. A good or bad day is not yet the result.
- 04Days 8–14
Compare weekly averages
Compare the first treatment week with baseline. For inter-cat tension, record staring, blocking, chasing and access to resources rather than only fights.
- 05Days 15–28
Protect consistency
Keep resources and routines stable. Reward use of preferred scratching, resting and litter areas; do not punish accidents or normal scratching.
- 06Day 30
Continue, redesign or stop
Calculate the change. Continue only if the improvement is meaningful enough to justify the recurring cost. If not, revisit diagnosis, environment and professional support.
Medical boundary
Do not label a sudden change “stress” from a search result
Urination, appetite, pain, mobility and hiding can change because the cat is unwell. A plug-in may be an adjunct after assessment; it is never a diagnostic test.
Straining with little or no urine
Repeated litter-box visits, vocalising, distress or inability to pass urine require urgent veterinary care, especially in a male cat.
Sudden urine or appetite change
Blood, pain, weight loss, vomiting, lethargy or a new elimination pattern belongs in a medical assessment before a diffuser trial.
Persistent fear or injury
Chronic hiding, escalating attacks, blocked access or wounds require a structured plan with the veterinarian or qualified feline behaviour professional.
Decision questions
FELIWAY Classic vs Optimum FAQ
Is FELIWAY Optimum better than Classic?
Not proven across all cats or outcomes. Optimum is marketed for a broader mix of signs, while Classic has more direct diffuser evidence for unwanted scratching and older evidence for urine spraying. We found no independent head-to-head diffuser trial establishing universal superiority.
What is the main difference between FELIWAY Classic and Optimum?
Classic is positioned around a feline facial-pheromone message linked to territorial security. Optimum uses a newer pheromone complex and is marketed for a broader range of signs, including multi-cat tension. That is a difference in formulation and positioning, not a guaranteed difference in outcome.
Which FELIWAY should I try for scratching?
Classic is the narrower evidence-led starting hypothesis because a large placebo-controlled trial studied unwanted scratching. It should be paired with a stable, suitably tall scratching surface near the chosen site; scratching is normal behaviour and should be redirected, not eliminated.
Which FELIWAY is better for cats fighting?
Optimum is marketed for broader stress signs including tension, but no diffuser can replace separate litter, food, water, resting and escape resources. Persistent stalking, blocking, injury or chronic hiding deserves a veterinary behaviour plan.
How long should a FELIWAY trial last?
The manufacturer recommends at least one month and continuous use. A cleaner household test records seven baseline days, keeps one setup for 30 days and uses one predefined outcome to decide whether another refill is justified.
How many FELIWAY diffusers do I need?
The manufacturer states up to 700 sq ft for one open area. A closed floor plan, separate floors or rooms divided by closed doors may require separate zones even when the total home is smaller. Count airflow zones, not only total square footage.
Can I switch the diffuser off at night?
The official instructions say to leave it plugged in continuously. Switching it off changes exposure and makes the result harder to interpret.
Where should I plug in FELIWAY?
Use an unobstructed wall outlet in the cat's main room or the target-behaviour zone, with about 4 ft of clear space above. Avoid furniture, doors, curtains, shelves, extension cords, adapters and multi-plugs.
Does FELIWAY replace a vet visit for urine problems?
No. Sudden house-soiling, repeated trips to the litter box, straining, blood, pain, little or no urine, appetite loss or lethargy require veterinary assessment. Inability to pass urine is an emergency.
Why does Félinscope link to Amazon?
Amazon Associates is active for Félinscope in France, Belgium, the US, Canada, the UK and Ireland with OneLink. The button opens a FELIWAY selection rather than guaranteeing one exact kit. Verify Classic or Optimum, starter kit or refill, plug type, seller, price and returns after redirection.
Primary sources and evidence limits
Exact formula. Exact device. Exact outcome.
Félinscope did not physically test the diffusers over 30 days. We separated official instructions from published evidence and disclosed sponsor relationships where the paper reports them.
- FELIWAY US — Classic starter set · official positioning, 48 mL refill, suggested minimum duration and installation guidance.
- FELIWAY US — Optimum diffuser kit · official positioning, 30-day duration, 700 sq ft coverage and six-month head replacement.
- FELIWAY US — product FAQ · continuous use, placement, zone, outlet and hardware instructions.
- Journal of Feline Medicine and Surgery, 2023 — Classic scratching RCT · 1,060 cat–owner pairs, placebo response and sponsor disclosures.
- Journal of Feline Medicine and Surgery, 2001 — facial pheromone spraying trial · small double-blind placebo-controlled study.
- Journal of Feline Medicine and Surgery, 2018 — shelter diffuser RCT · no measured stress or upper-respiratory-disease benefit in that setting.
- Open Journal of Veterinary Medicine, 2021 — Optimum diffuser study · open-label, uncontrolled home-use evidence.
- Animals, 2024 — new pheromone complex collar RCT · controlled evidence for a prototype collar, not the wall diffuser.
- Journal of Feline Medicine and Surgery, 2018 — pheromone-therapy evidence review · study-design, setting and delivery-system context.
- FelineVMA — meeting the needs of indoor cats · five pillars of a healthy feline environment.
- FelineVMA — setting up for success · practical resource placement and household design.
- FelineVMA — 2024 intercat tension guidelines · recognition, prevention and management framework.