I wonder if they'll ever top the Botswana special. That has remained my favorite top gear episode by far (followed by the Polar special).
I preferred both the Polar and Vietnam specials.
That's not to say the Botswana challenge was bad by any stretch (OLIVER!!!!!), but I just hope they have a great challenge set up for this season (trying to remain spoiler-free, so I only know the absolute basics of what they have planned).