Do the franchises back up the claims of toyota l/100 km that are printed on the brochures?
and the expected service life too?
Ive said this before - where companies are held liable for delivery of a service performance (e.g. USA has 60,000 miles (100,000 kms) power train warranty. They only fill the correct spec oils.
e.g. old corolla (1ZZ-FE) used 5w30, newer one get 0w20, pre 2010 camry 4 cyl used 5w30, post 2010 uses 0w20.
at the time of introduction, the cost difference of 0w20 to 5w30 was 3 times - so toyota bundled the first 5 oil changes free of charge.
when no warranty or responsbility - you can use whatever you want, might as well put coroli corn oil or axle grease in there - Toyota wont care (just like Pakistan - IMC will cancel your powertrain warranty if you even passed gas in the driver seat) - they know that customers are naive - so they can sell 30w60, 5w50, 10w100 etc etc. - It doesnt mean that they spec it.
So get to the manufacturer and burden some responsibility of them, you will get the truth.
btw - is the delta T in Oman really that bad? - meaning you guys have 75C weather in daytime?