Rich McCormick writing for The Verge:
[Motor Trend] says that Android Auto tracks variables including vehicle speed, throttle position, fluid temperatures, and engine revs, information that is collated and then sent back to Google. Apple’s CarPlay, on the other hand, only checks with the car’s powertrain control module to ensure that the vehicle is moving. Porsche was apparently unwilling to enter a deal that would send reams of information back to Google — partly, Motor Trend says, because the manufacturer thinks those details make its high-end autos special, and partly because Google itself is in the midst of building its own car.
I can’t possibly imagine why Google would want all that data. Can you?