Just about anywhere surfaces mate. Prime culprits are oil pan gasket, valve cover gaskets, front and rear crankshaft seals. Have your mechanic add some fluorescent dye to the oil and find the leak with a black light.
You have an oil leak.
That would depend on what oil seal you are referring to. There are many oil seals.
You either have a leak or it is burning oil.
antifreeze leaking into the oil pan
Try coating the area with talcum powder to determine where leak originates
There are several causes of oil leaks in a 1998 Buick Skylark. It could be a gasket, a bad seal, or even a drain plug.
My friend you have a leak. You are going to have to crawl under the car and find the leak.
Maybe oil passage leak by gasket in timing cover
A head gasket leak. I had one, its not fun
wash all the oil off then start the engine and watch for new oil Oil pressure sensor or oil pan gasket!
head gasket may need to be replaced
There is a seal to seal the pan to the block. This seal goes out mostly do to lack of oil changes. Change oil then add a stop seal leak additive that closes off the leak with no harm to the engine. It works!