It is most likely either transmission fluid or power steering fluid.
This is called the grease gland, and it is only found in male guinea pigs. It is a scent gland, and it is perfectly normal for it to be oily under the fur in this spot. The grease gland should be left alone unless it becomes clogged and infected. This doesn't happen often, but if you suspect a problem, take your piggy to an exotics-specialized vet.
It can be a noun, meaning a speck, coloration, stain, or location. It can also be a verb, to spot, meaning to notice.
Rub the food on a brown paper bag. If it leaves an oily spot that does not dry, it contains fat.
It could mean that there is a leak in the system near the spot. The system cycles oil with the refrigerant, and when the refrigerant escapes through a leak it can release oil, which will leave an oil spot.
I would say the forehead, because it is the most oily spot on the face.
That is called spotting. Women often spot the day before or a few days after their period.
You'll notice a tiny spot of blood on her vagina.
The spot light Effect
i think that is alopecia.. now search alopecia.. ^_^
What are the Spot Resolutions from Abe Lincoln?
Under the bed
Spot the dragon .