Oil leak.........

I don't know specifically of your van but will give a couple options.

Sometimes the engine oil will be routed to the radiator to be cooled within the radiator. You can see this by oil cooler lines (smaller steel lines) going to the side tank of the rad.

Sometimes power steering fluid will be cooled by a p/s oil line being routed under the front crossmember (which your rad sits above). - so check your power steering fluid level too!

Either of these lines could be leaking.

Your van has a transverse mounted engine putting the front and rear seals to the right and left.

It is best if you can put paper under your vehicle to see exactly where it is dripping from and work backwards. Sometimes running the vehicle will develop the oil to leak so you can actually see it. Try not to fix things until you know what is going on, it is better not to add additives if you can help it (and is cheaper in the long run)

When the VW diesel's first came out the running joke at the dealership was that the owners could take the money they save on fuel the first year and get a gravel driveway so that when it started to leak in the second year they wouldn't notice ;-)

PS let us know the colour of fluid leaking. Red, ATF, Clear Brown/Black Engine oil, Clear with Aluminum filings in it (power steering fluid). etc..

Agreed. You need to look closer where it's coming from too. Put you head under there and look carefully. Put your finger on a drop to check the color as noted. That's better than testing it off the floor. I never had any luck with oil leak stoppers. One reason they tell you it takes 75 miles to work is because they hope you are 75 miles away from them when you still have the leak.

With your knowledge of cars you would be better off taking it to a local service rep and have him diagnose it and give you an estimate to fix it. It could be anything on the engine. You can't guess it away and have to look at the engine to determine where it is coming from.