correct. The car can come in for 6 months (180 days in a calendar year) and then must stay out for 6 months before coming in again. But that only works if you are on a tourist visa, doesnt work if you have a residence.
If you have had a residence for say 3 months, then you bring the car in then the car can only stay for 3 months and then must be out untill you are back on a tourist visa again.
Best way is for the non owner of the car to get a residence and the owner of the car come in on a tourist visa, but then after 3 months you would need to do a border jump and you cant jump the border with a car on your passport unless you drive it across.