In the 1979 recoding tank wagons that carried 'White Products' were grouped into the VTQx classes.
The classes were VTQA, VTQF, VTQY, VTQX
Most tank wagons in the VTQx group were allowed 95km/hr when empty but only 80km/hr when loaded.
In 1987/1988 the VTQY class was relettered to VTQF.