I thought the previous owner spilled oil in the back cause it looked pretty new oil. So I cleaned it up and it appears to be back. I was a pretty good puddle when I found it and I got as much as I could out of the seat but maybe it is remanates left over from the seat sopping out. I just wanted to ask the experts if I should be worried and also if anyone had any ideas of what it could be?

My thought is leaking gas filter as it is on the passenger side. If it is I will replace it right away. I may drive the car without a backseat for a while to see if the seal is leaking.
What are anyones thoughts?

 

There is no oil near the back seat in the mini. Probably spilled on the seat would me my best guess like you said.