You can get Alexa in your car with Echo Auto, but there are a bunch of other ways, including that extra Dot you might have laying around.
Echo Auto-Hands-Free Alexa In Your Car With Your Phone, AYOUB COMPUTERS
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How to Install Alexa in your car Alexa and Echo in your car.
s Alexa app will soon work as an in-car display for the Echo Auto - The Verge
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Hyundai Adds Blue Link Skill For Alexa
Complete Guide to Integrating Alexa Into Your Car - AskMen
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How to use Alexa in a car - Quora
How to Get Alexa in Your Car