Somewhere on vw.com under "owners", there is an updated oil recommendation saying that 1998-2004(?) gasoline engine VWs in the US should use VW 502.00 rated oil, preferably 5W-40 (all such oils available in the US are synthetic). For 1996-2003 diesel engine VWs, a 5W-40 synthetic oil meeting the requirements listed in the owner's manual is recommended (VW 505.00, ACEA B3 or B4, or API CF-4, CG-4, CH-4, or CI-4). 2004 and newer VW diesel engines in the US need VW 505.01 rated oil.
There are no oil lines on the cooler, you need special *coolant hoses* to make it work. Only other thing you'd need to add it back in would be a longer threaded nipple for the oil filter (the cooler is held on by a nut on the same nipple that the filter screws on to.)
I'm guessing yours is missing because it probably blew. I've never had one go on me but I have heard that this is not uncommon, and it used to fake people out into thinking they'd lost a head gasket and probably some otherwise good cars were unnecessarily retired. I do *like* the cooler however - it's a simple, elegant design and provides not only cooling of the oil but helps the oil warm up *faster* in cold weather, too - as evidenced by the oil temp. gauge on my '84 GTI (did not have cooler on it when I bought it, but I added one from an '84 GLI shortly thereafter. My cruise oil temp dropped about 10 degrees C and the oil did warm up noticeably faster.) I actually prefer this setup to an air-to-oil cooler with a thermostat because of the faster warm up and greater simplicity.
If you're having a flickering oil light, are you running at least a 40 weight oil? VW 4-cylinders, even the new ones, like the heavy oil. (owner's manual even says so!)
Thanks for the great info about the oil cooler. Very helpful. I am shopping for one now. Found one online at Autohaus Arizona for about $65 including the o-ring, but I will also have to find a longer nipple, as you said.
I use 20W50 oil because of the high mileage (260,000 miles) on this vehicle.
Now that I think about it, I think you may need the little thing on the head that looks like a thermostat housing (but is just a flange, because the VW uses an upside down cooling system) the one with the sensors in it - with the oil cooler it has an extra hose fitting I think? it's been so long since I've done this conversion that it is getting some what furry.
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