If you're looking for the best car diffuser, check out the Syntus Essential Oil Diffuser. This oil diffuser holds 50ml of liquid, has a waterless auto shut off feature, and is powered by a USB cord, so you can plug it into a USB car adapter, a wall charger, or run it off of a portable power bank.\r\n\r\nWhy We Like It - Syntus Ultrasonic Essential Oil Diffuser\r\nThe Syntus Ultrasonic Essential Oil Diffuser is a USB powered diffuser, humidifier, and air freshener. It offers both continuous and intermittent spray modes, and will automatically shut off when it is running low on water to prevent dry burning.\r\n\r\nPerformance\r\nThe Syntus Essential Oil Diffuser is perfect for use in your car or home office. Syntus essential oil diffusers have both continuous and intermittent modes, so you can adjust the mode to the size of the environment. It has easy-to-use power buttons, a green power light on top, and even has an auto shut-off feature for when it is running low on water. If you don't like the features of this device, another great oil diffuser ultrasonic aromatherapy device is our #1 pick, the InnoGear Essential Refresher Ultrasonic Aromatherapy Diffuser.\r\nDesign\r\nThere's nothing special about the design of this diffuser. Ultrasonic aromatherapy diffusers are usually made to fit in a cup holder, and this model is no exception. Thankfully, it runs off of USB power, not a proprietary car charger, so you can use it anywhere that you can hook up a USB cord, such as near your laptop or an outlet. Unfortunately, even though it runs on USB power it isn't capable of charging your phone. If you want an essential oil diffuser ultrasonic device that can also charge your phone, check out the Gulaki Diffuser Essential Oils Multifunction instead.\r\nValue\r\nIf you\u2019re looking for an extremely cheap option, consider the RoyAroma Aromatherapy Essential Stainless Freshener, which is one of the many related products that is electricity-free. However, if you decide to go with the Syntus model, you will be happy to know that it will only set you back $15.99, and that includes free shipping! As usual, there is no warranty, but this model has received good customer reviews overall, scoring 4.2\/5 stars on Amazon. Some people have reported it failing after use, but thankfully that problem doesn't seem to be widespread.\r\nSyntus Ultrasonic Essential Oil Diffuser Wrap Up\r\nThe Syntus Ultrasonic Essential Oil Diffuser is one of the many affordable options for car diffusers. Like many other models, it fits in your cup holder, works as both a diffuser and a humidifier, and is powered by a USB cord. There is nothing particularly great about this product, but besides its small 50ml maximum capacity, it doesn't have any significant downsides either.