Dash is compatible with any car that has an OBD-II port. That's short for "On-board Diagnostics, version 2," and it's been required on every passenger car sold new in the US since 1996; in fact most cars worldwide have had this feature since then, though it wasn't required until later in many countries.
This port is what your mechanic uses to connect to your car's computer when your "Check Engine" light comes on, or when you take your car in for inspection.
This means unless you're still driving that Mustang fastback from the 1970s, or that 80s LeBaron convertible, it's pretty likely that your car will work with Dash.
There is one caveat: drivers of electric vehicles probably won't get the full Dash experience; we need more data on how those cars work before we can give those cars accurate scores. The fuel economy calculations and scores for diesels and some hybrid vehicles may be a bit off as well, but most are working very well.