I haven't read the whole thread. But here are a couple of relevant reasons for this shorter oil change interval.
Its better to keep intervals at 5000kms for PKDM small cars especially 1000cc +/- engines. Because until recently most of them were carburetted small engines, low power, running hot all the time from being pushed in hot weather. (remember mehran & bolan we still have those dinosaurs)
Engine build quality here is lower than abroad
Oil quality here is lower than abroad
Fake oils are very prevalent
No oil testing body, no data is published for most local engine oils, most imported oils are either grey imports or sold from unauthorised dealers (who knows whats their MFG date? Expired?)
Petrol is of lower quality resulting in poor emissions, more carbon deposits inside the engine
I would use a genuine, imported 100% synthetic engine oil for 10,000kms in my car IF my car was 1800cc or above PKDM car. Otherwise I will prefer changing it earlier. Also remember that 10,000 or 20,000kms change interval recommended by some manufacturers is not recommended by several mechanics (internationally) who have seen the internals of those engines. A lot of mechanics would recommend you to change the oil earlier if you want your car running for longer. 10,000kms is over stretching it and taking unnecessary risk for some people.
Plus in case of most local cars and oils, you can feel the engine getting noisier and the car running rougher just after 3000-4000 kms. If you use a better oil (imported synthetic), that roughness kicks in a couple of 1000kms later. But it still kicks in much before the 10,000kms interval. Hence, I'd like to change my oil before I feel any sort of change in engine noise or roughness. Changing engine oil a few 1000kms early does not make any considerable difference on your pocket but it does improve your engine life.
If you check manuals of newer cars, they come with 10,000kms interval recommendation. Older cars were recommended at 5,000kms. Pakistan did not have synthetic oils available until recently. Mechanics and people did not know any difference between mineral oil, semi synthetic, fully synthetic and 100% synthetic. Everyone was using Havoline 20w50 in their cars a short while ago! In hind sight, it was a very nice recommendation by whoever recommended that to just simply keep a shorter oil change interval. Even with fake engine oils car would survive 5000kms, even a meharan with 20w50 Havoline (real or fake) with AC, in summers and extra fortified mineral infused + goodness of gutter infused tap water running in its radiator would survive a 5000kms change but it definitely wont last 10,000km changes!
