I let my friend use my car to manage my rental property only. Can I deduct the car expense on my tax return

[Carl]

If the vehicle was used 100% for this, then no problem. If used for less than 100%, then you can only claim the "per mile" deduction. Hopefully, you kept detailed mileage records of business use and personal use miles.

But generally speaking, when you only own say, 1-3 rental properties, claiming vehicle use is an absolute waste of time because it will not help you one single penny on your tax liability. That's because it's rather rare for rental property to show a taxable income on paper. Especially if you have  a mortgage on the property. It's more common for rental property to show ever increasing passive losses every year, that just continue to grow each year and get carried over.