Car Diffusers: What You Should Know

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Guide to buying a car diffuserWhenever something is popular, as essential oils are right now, it seems like people clamor for their corner of the market. People own multiple diffusers for different areas of their homes, diffuse at work or school, wear aromatherapy jewelry, and diffuse in their cars.

Is it all too much? While diffusion is generally safe, there is no need to be diffusing non-stop. Your nose needs a break once in a while, and there is no therapeutic advantage to diffusing more than 10 minutes, 3 times a day (nebulizers) or 30-60 minutes, 3 times a day if you own an ultrasonic. So the first question is do you even need a car diffuser?

Do you need a car diffuser?

As with most things, this will depend on your individual circumstances. You will need to evaluate where else in your life you are diffusing or using essential oils and if you need to diffuse in your car as well. The recommended daily diffusion times given above can help you decide.

Some reasons why you may want a car diffuser include:

  • You want to promote alertness and mental clarity while driving
  • Your kids smelly gym socks are still in the back seat
  • You want to diffuse uplifting, feel good scents to put you in the right frame of mind to face wherever you are going to
  • You work in an public space with lots of germs, but can’t use a diffuser at work (e.g. teachers, health care workers, daycares..) and want to diffuse on your commute instead as an ounce of prevention

What are the cautions for car diffusers?

Avoid oils that could make you drowsy: You need to exercise some caution with car diffusers. Certain scents should be avoided while driving, especially clary sage, sweet marjoram, chamomile and sandalwood. For more details on what oils to diffuse in the car see Essential oils for Driving 

Don’t block your vision: Another caution is not to hang anything from the rear view mirror or anywhere else where it may interfere with vision. This is especially true of metallic or reflective objects (like a stainless steel diffuser necklace). In some areas, hanging something from your rear view mirror is illegal.

Limit diffusion time in closed spaces: What makes diffusion generally so safe is that the oils are dispersed into a large volume of air in the room. In a car, we have a small closed space. Therefore, using a diffuser that sends out a constant mist into a small area for a prolonged time is not recommended. An ideal car diffuser should be able to be unplugged, turned off, or put away. If that isn’t possible and you are driving for longer than 30 minutes, you may want to give yourself a break from the scent by opening the windows.

What are the best diffusers for a car?

The ideal diffuser for a car is one that:

  • Does not emit an overpowering scent or large volume of mist
  • Can be turned off so you can take a break from the scent
  • Won’t interfere with your ability to safely drive a car

Here is the bad news, I have not come across the ideal car diffuser. Car diffusers tend to be passive diffusers—some sort of pad or clay piece that absorbs the oils and lets them evaporate into the air. There are some diffusers which are small ultrasonics, and I have even seen nebulizers marketed for cars.  I can’t recommend a nebulizer for a small space like a car.

Passive diffusers cannot be turned off. Heated passive diffusers can be unplugged, but the scent pad will continue to evaporate essential oils. Passive diffusers are generally safer than ultrasonics car diffusers because the amount of oil diffused will be less.

Let’s examine some specific models.

Product NameTypeCan be turned off?Uses heat?
Car ScenterPassive
Terra Cotta PendantsPassive
Ultrasonic Car DiffuserUltrasonic
Innogear USB DiffuserMisting
Breezy Vent ClipPassive

The Car Scenter

The Car Scenter  (affiliate link, Amazon) is one of the original car diffusers. It is a passive diffuser that uses scent pads.  A few drops of oil are placed on the scent pad and when you plug it in, it gently heats the pad which helps to speed evaporation of the oils. Similar in design and function is the Diffuser World Traveler car diffuser.


  • easy to change the scent as pads can be replaced
  • inexpensive
  • you can take a break from the scent by unplugging it and placing it in your glove box


  • requires buying refill pads occasionally (but they can be used more than once)

TerraCotta Pendants Car Diffuser

Terra Cotta Pendants (affiliate link) in Canada make high quality aromatherapy jewelry. The finish on their terracotta is the best I have come across. For their line of car pendants, they offer the same terracotta medallions on a shorter cotton cord. Originally you needed to tie the cord to hang it, but now they come with a magnetic clasp which makes it much easier to remove and refill.

The clay only needs a drop or two of oil. Depending on the oil you use, the scent may linger for a few days. Middle and base note oils will last longer. This is what I use when I diffuse in my car.

terracotta diffuser pendant


  • Pretty, non-reflective surface won’t catch the light while driving
  • Magnetic clasp makes it easy to hang and remove
  • Requires very little oil
  • Does not need replacement pads


  • May be difficult to find a place to hang it from (if you are a law abiding citizen)
  • to change scents, you need to let the current one fade
  • needs a little cleaning once in a while to keep its absorbency optimal
  • it can’t be turned off-scent may be too much over a long trip

Ultrasonic Car Diffuser

The ultrasonic mister diffuser plugs in to your 12 V /cigarette lighter. It has a scent wick as well as a (water) reservoir. Once plugged in, it emits a fragrant mist. It does have a power control so it is possible to turn it off when you have had enough.  This product is private labeled by multiple companies, and is also available directly from Asia on both Amazon and Ebay under different brand names.  Overall, customer satisfaction is mixed but malfunctions or difficulties using it make me hesistant to recommend it.


  • Can be turned off when you don’t want to use it
  • Inexpensive


  • Creates a lot of mist which may blow towards your face while driving, scent your clothing (bad if you work in a fragrance free workplace), or land on your upholstery

New at Plant Therapy! The Diffuse on the Move Diffuser!

InnoGear USB Car Diffuser

If you want an ultrasonic diffuser for your car, a better bet is the InnoGear USB Car Diffuser (affiliate link, Amazon). It is shaped like a travel mug and will fit in your car holder. It works like a traditional ultrasonic—just add water and a few drops of oil. It also has the option to run continuously, or intermittently. I would have preferred if the intermittent setting was longer than 30 seconds. This plugs into a USB outlet, so if your car doesn’t have one, you will need to get an adapter to plug it in to your 12V. Aroma2Go has inexpensive ones in several colors.

Now, there is one more thing I need to say and if you have read any of my other posts, you know I really dislike the colored lights on diffusers. Yes, this is a car diffuser with seven color changing lights to provide mood while you are driving. This could be dangerous if the lights create reflections on the window.


  • Has intermittent setting
  • You can take it into your home or office and use it anywhere you can plug it into a USB outlet
  • Simple to change scents


  • Requires a USB outlet, or you must separately purchase an adapter
  • Intermittent setting isn’t long enough
  • Unnecessary and potentially distracting LED lights

Breezy Vent Clip

The Breezy is a vent clip diffuser, but not like you’d expect. The video below better shows how it works, but basically you put several drops of essential oil into the included 5 ml bottle, attach an orifice reducer, and then insert a cotton wick through the orifice. You then screw this all into the vent clip device. The oil is wicked up through the cotton and air from your vent blows over it. One nice feature is that you can adjust how much air flows through the clip. I have not had a chance to try this one personally, but I would be curious to know whether the weight of a glass bottle would pull down on the vent—closing the car vent or causing the whole vent clip to sag? If you have one, please let us know what you think in the comments.


  • No heat, uses simple evaporation from the air coming through your vents


  • Changing scents could be cumbersome as you need to remove the wick and orifice as well as potentially clean the bottle out, or have a set of spares.

The Verdict

Our top pick? Despite all the new designs that have emerged in recent years, the Car Scenter (affiliate link, Amazon) or the equivalent Traveler (affiliate link, Diffuser World) is still the best bet as the scent can easily be changed, and you can unplug it and stow it to give yourself a break from the scent.  If you only will be using it on shorter trips (<30 minutes) the Terra Cotta car diffuser is less expensive in the long run as you never need to purchase refills.

If you want to DIY it, a simple wooden clothespin with a few drops of oil on it clipped to your vents is the easiest and least expensive way to diffuse in your car. You can even set aside a few clothespins so you can rotate scents easily.

What about you? Do you diffuse in your car? What is your experience?

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