oil leakage

these cares have a problem with the oil filter adapter housing gasket (sounds complicated but you will need to now if you need the gasket) & from the timing cover. if you try to tighten the bolts on both you can likely find wich one is leaking because the bolts will have loosened after the gasket beneath them degraded

If the oil filter has just been replaced on your 1995 Buick LeSabre it is possible the gasket from the old filter was left on the filter sealing surface when the new filter was installed. You can try removing the oil filter for inspection. There should be a sealing gasket on the filter and a bare metal surface where the filter gasket seals. When reinstalling the filter do not over tighten it, about 1/2 turn after the seal contacts the base should be sufficient.