I dealt with this for a long time...and finally cleared it up. What you're talking about is the charge air hose (or system)...from the throttle, hot air is recirulated through the oil cooler's air hose section (right behind the radiator) and comes out from the bottom of it on the driver's side. This is the lowest part of this system and a lot of oil condenses there. It is very normal. From there, the charged air runs up over the engine and to the top of the turbo where it is added to the air coming from the MAF and air filter box. Usually by the time the air gets to the turbo it no longer has oil in it. The lowest point where there's a rubber hose on my car was saturated and the hose was soft ('98 S70) so I replaced that hose for good measure last weekend.

I'm more concerned about the oil blow by on the cool side of my turbo coming from the air filter box and MAF where some smaller PCV (positive crankcase ventilation) hoses also attach. Seems there's a nipple there that lets some more air into the turbo while recirculating the condensed oil, sending it to the oil trap (under the manifold) which separates the oil and gases and sends the oil back into the engine and the hot air along with throttled air back arond to the oil cooler's protion of the charged air system again.

If you know about the blow-by on the side of the turbo (some say it's normal, but I don't want to agree with that), please post and let me know.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.