Unique identifier representing the service type. The following values are valid: 1 - Air Filter Replacement, 2 - Brake Inspection, 3 - Battery Inspection, 4 - Engine/Drive Belt Replacement, 5 - Engine Coolant Replacement, 6 - Engine Oil Replacement, 7 - Fuel Filter Replacement, 8 - General Service, 9 - Lubricate Chassis, 10 - Radiator Flush, 11 - Rear Axle Fluid Replacement, 12 - Spark Plug Replacement, 13 - Tire Rotation, 14 - Tire Replacement, 15 - Transmission Fluid Replacement, 16 - Wheel Alignment, 17 - Safety Inspection, 18 - DOT Inspection, 19 - Miscellaneous - Parts, 20 - Crane Inspection, 21 - Dielectric Testing Inspection, 22 - IFTA Updates, 23 - Public Service Commission inspection, 24 - External Annual Vehicle inspection