firstly lets get a control specification here.
the useless and scrapped JDM orphan cars you see roaming in Pakistan cannot work on the fuel available in Pakistan beacuse they are tuned to a fuel type available in Japan only - its not an alien concept but quite well known around the world. The same problem occurs with the "UK origin gray import" mercedes benz, BMW, Audi, Porsche etc vehicles - both petrol and diesel.
then pile on top of this madness the use of wrong engine oils which proceed to completely mess up the exhaust system - specially new euro diesels which require a very specific engine oil to keep the exhaust oxidiser in healthy shape.
the only qualitative report you can get is from cars made to standards that are existant in Pakistan, e.g. products sold via Indus Motor Co. Ltd, Atlas Honda Motorcars, Pakistan suzuki motors, Gandhara Nissan Ltd, Shahnawaz Ltd (MB). - little example is to plot out the ECU control on the Pakistani cars and then also on similar japanese scrapped parts import.
The usual average guy owning an "aasum" jaydee amm" car complete with pikachu stickers and engine smaller than a kitchen blender dont have any say in this analysis due to the reasons mentioned above.
to answer the guy asking why diesel cars are not sold in Pakistan is purely due to the price of diesel fuel, when it was cheap @ Rs 5/litre people didnt care if their car was returning 3 km/lit because it was dirt cheap - there is also a lack of diesel mechanics and injection system repair facilities in Pakistan - usual Hz ustaad RA mechanic would say - "jee aisa set karenge ke hawaa ki tarah jeygei gaddi" - the all holy qibla Hz ustaad RA mechanics words are the final say for any car owner - the service manual is "raddi" and "bewaqoof bananay ka tareeqa"
diesel cars can return incredible mileage - specially new direct injection ones - they cannot run in Pakistan due to the lack of technical knowledge and education to repair them (e.g. toyota 1KD-FTV) - its a given that toyota screwed up the injection system design but all mechanics do is throw junked parts at it and pray it works.