1996 Ford Mustang Owner's Manual - Page 294

NOTE: Rear axle lube quantities must be replaced every 100,000 miles (160,000 km) or if the axle has been submerged in water. Otherwise, the lube should not be checked or changed unless a leak is suspected or repair required. Motorcraft Parts If a spark plug is removed for examination, it must be reinstalled in the same cylinder. For 3.8L engines: Cylinders #1, #2, #3 have an EG suffix. Cylinders #4, #5, #6 have an E suffix. For 4.6L (2V) engines: Cylinders #1, #2, #3, #4 have a PG suffix. Cylinders #5, #6, #7, #8 have a P suffix. If a spark plug needs to be replaced, use only spark plugs with the service number suffix letter as shown on the engine decal. 300