A 1997 Ford E350's recommended oil type depends on the engine it has. Ford E-350s from that year came with several different engine options (gasoline and diesel). You
must check your owner's manual to determine the correct oil type and viscosity for your specific engine.
The manual will specify the oil's viscosity (like 5W-30, 10W-40, etc.) and whether it should be conventional, synthetic blend, or full synthetic. Without knowing your engine, any recommendation I give could be incorrect and potentially harm your engine.
