I found this interesting note on the Texas Dept. of Public Safety vehicles, (State Troopers)
Texas Department of Public Safety
The Texas Department of Public Safety is another example where centralized service facilities don’t exist except at the state capitol, Austin. A second facility is scheduled to open up in Houston.
Maintenance responsibilities currently rest on the operator’s shoulders and a supervisor verifies proper preventative maintenance procedures, which are entered into its fleet database. It is suggested that troopers utilize a dealership for servicing, but that is not always possible. In some cases, such as West Texas, where service facilities are few and far between, the trooper may conduct his own vehicle maintenance.
Texas DPS recommends that a quality brand of oil be utilized in the weights recommended by the factory for that particular vehicle. Black and white pursuit vehicles are required to abide by the severe-service maintenance schedule. Texas DPS is now allowing districts to use synthetic oil and an extended drain cycle, however, the oil must be analyzed periodically to determine the optimum drain schedule.