do u know even more than required frequent oil changes harm the engine. we had a 98 corolla which we bought zero meter. sold it in 2007 after running it for 1 lac 20 thousand kilometer. we always used to change the oil at 4500 km, sometimes even more than 5000 km, that too the shell yellow oil, and even when we sold, its engine was in perfect condition. i remember it used to hit 130 in 3rd gear. this 2000 and 2500 km oil change theory is just a myth by local vendors here in pakistan who want to loot us. the booklet of 98 XE said to change the oil at 10000 km, so how can we say 2000 km. now u wud say the dust and all in the country. well, when they designed the car, they knew it wud be run in all kinda environments, and i m more than sure that they must have kept tolerance in 10000 km as well. i personally think to change the oil before 4500 km is like being criminal to ur car