Other than the obvious legal problems, insurance issues, etc., which you need to thoroughly understand and be prepared to pay for, it is NOT good for a car to be in storage. Especially, it is not good for a car to be in storage, without being prepared for storage.
That includes such things as driving the car for about 20 miles to get it warmed up and then immediately, draining the oil and changing the filer and adding new oil. That will include getting the car up off the ground. That will include doing something to the Shock Absorbers, so they are not bearing the weight. That may include changing the Brake Fluid and the Transmission fluid.
A car that is in storage will deteriorate faster than a car that is in (near) daily use and IMO will be more problematic and dangerous than a car that has been in (near) daily use.
I would think long and hard before loaning a car to someone for one day, let alone for months.
Begin with your insurance company and see what they have to say about the ramifications of this. Then, think about the other issues.
Edited by Lanny, 13 September 2017 - 02:06 PM.