I have done 4 trips to Lahore / Islamabad in the past year from Karachi. I don't have a turbo vehicle but had good mileage and experience with the following:
* Fuel up from your trusted pump in ISB, next refill should actually be on M4 but since I don't know of a good pump, I refilled at Bhera from Hascol I think.
* Towards Multan, I only filled once I reached Multan (stopped for food once, and an overnight stop the other time). I think it was PSO right after getting off one of the interchanges.
* On M5, I have good experience with GO fuel stations and have refilled many times from there, both ways. I think there are 2-3 on each side.
* Fill up from PSO that is right outside Sukkur, have used that a few times.
* Shell Moro mentioned above is a good idea but I think Taj also has their own pumps, which should also be ok. Used them 1-2 times. I have not had good experience with Shell Gambat going northwards (1-2 kmpl lower than expected mileage on that tank).
* You should not need another fill up till Karachi, but if you want to be extra careful, than the PSO in the beginning of M9 is a good option.
