How long do you want your change interval to be?
Do you know if the previous owner took care of it?
What does the manuel call for?
If it was mine, I would probably stick with a few 4-5k mile runs on dino 5w20 and see how it does. Any name brand would do.
If you know the previous maintenance history that can tell us alot. Maybe do an Auto RX run in both engine and tranny.
At 43k I would probably have the transmission fluid changed out.