Are they telling the same thing or is there any subtle difference between them? thanks.
The use of each phrase is valid under specific circumstances.
Get out of my car is used when the person saying it is inside the car and telling someone else (who is also in the car) to get out. Usually this is said with a negative tone.
Get out from my car is weirdly worded. Get out from UNDER my car is used. Would suggest never using Get out from my car.
The only difference I can see is that "get out from my car" is not how English is generally spoken. It's meaning is clear enough, but it sounds non-idomatic. Everyone I know would say "get out of my car".
Here is a non scholarly reference ;)