Hi there, gautreaux.
Thanks for taking the time to post about mileage tracking in QBO.
Currently, the Rule feature is not available for mileage, but in Banking. I recommend submitting feedback from your QBO company so our engineers know you need this option. Just click on the Gear icon and choose Feedback.
Here is an article for your additional reference: Automatically track mileage in QuickBooks Online.
Let me know if you need more help.