Where is the full filter located on a 1991 Cadillac Seville?

The 1991 Cadillac Seville's full filter (which I assume you mean the full-flow oil filter) is typically located on the driver's side of the engine block. However, the exact location can vary slightly depending on the engine (4.5L or 4.9L V8). To be certain, you should consult your owner's manual or a repair manual specific to your vehicle's year and engine type. A visual inspection after locating the engine compartment will also help. Look for a cylindrical canister-like filter, likely near the oil pan.