The referenced DAWN article doesn’t mention it, but the PakWheels article on the same topic https://www.pakwheels.com/blog/petrol-shortage-may-sparks-amid-supply-disruption/ says that “they have called for an increase in freight charges, a measure aimed at aiding old vehicles back into operation“.

From what I get, there isn’t a ban on the age of the vehicle, but the older vehicles have high fuel consumption and it would be a direct side effect of the increase in freight charges that older vehicles will also become feasible.

the association also wants to permit the use of outdated vehicles for oil transportation.