i have changed my motor from 1300cc to 1500cc as my old engine was done for '' a Mitsubishi lancer 1998 '' the mechanic used Mannol safari 20w50 SN rated mineral oil '' i live in Egypt temp never goes below 10 Celsius and at summer it reaches over 40 Celsius '' for the 1st 1000KM to help clean and test the new engine and it was fine then changed again with the same oil and recommended to change it every 4000KM as our roads are dusty and heavily crowded, i wanna shoot for extra protection i want the best oil i could put into the car i wanna try full synth oil and the only full synth oil that comes in that 20w50 grade is Amsoil premium protection, now the question is should i change for Amsoil and extend the drain interval to 10000KM will it give more protection to the engine component and better flow ? my summer driving is mostly traveling for long long distances on a high RPM while mostly at winter its normal driving, is the change worth the money that will be spent ?