Oil Loss/Consumption/Pressure issue : Could it be Rear Main Seal?

[Hayes Myers]

Put the car on stands to get underneath and take a look.   Behind the rear
main seal there is oil streaming along the length of the tranny.  Looks like
it has cleaned up the tranny nicely. (is that a sign of the leak ?)   I'm
wondering if a rear main could cause loss of 1 litre of oil in 500km along
with the oil pressure indication issue? 

 

I was seeing fluctuating oil pressure with drops  below 2 at idle.and
starting near full pressure on gauge and simply bleeds off pressure as the
car warms up.

 

91 TQM 200 10v