I use my own LLC to manage multiple rental properties. When deducting mileages can I just lump all mileages together and report that under my LLC?

Since your LLC is in the business of managing the rental properties, you should report the miles driven for business on your LLC return (Schedule C or other as applicable).

To enter your mileage in TurboTax Online you can follow these steps:

1. Using the magnifying glass at the top of the page search for Schedule C
2. Click Edit or Add if you haven't entered your self-employed income yet
   •  be sure to include Vehicle as an expense type when you are adding expenses
3. If Vehicle is not an expense category listed scroll to the bottom of the page and click Add expenses for this work and choose Vehicle
4. Click Start next to Vehicle on the list of expenses and answer the questions with your information

That's good. A follow-up question. My LLC is a disregarded entity. while all the income is passed on to my SSN and treated as separate rentals, is it OK for me to record mileage under the LLC?

If you are "in the business" of running rentals, even though your income derives from the rentals themselves, it would be appropriate to have business expenses that are not directly attributable to the rentals, otherwise known as overhead expenses.  A rental property itself is not eligible to report business miles so reporting any overhead costs on Schedule C is the correct way to report.

@ScottTX