I own a year 2008 Myvi, all the mean while I am taking my car to P2 SC for the service using the P2 semi-syn oil (the SL grade). Since the car warranty had expired recently, I am thinking to service my car at any outside garage.

Is advisable to change to fully synthetic oil like amsoil asl or castrol edge? I heard from my friend that amsoil lubricant oil is quite good.

Since my Myvi is manual transmission type, do there have any gear oil in my car manual transmission gear box and do we needs to change the manual transmission oil?

Mostly 1 month will run about 2000~2500km, i change the oil about each 2 month. That's why my friend is telling me to use fully synthetic oil but I am not sure whether it is suitable or not...

then how about the oil filter? the normal oil filter should not be lasting for such a long time, right? can recommend any good oil filter as i am thinking of using amsoil asl now coz i will doing sales next month and i estimated will be traveling more than 4000km per month...

I think I will go with Amsoil ASL and I am waiting for my friend to help me to find a better performance filter for me, may be can last for 10000~15000 km...
I saw the ASL from Amsoil website that it can last for 15000~25000 miles, which means about 24000~40000 km... I have calculated and found that fully-syn will save more money than using semi-syn or mineral oil and give better protection as well...

just i don't want to waste time to change the filter in the 5000km interval, change a performance filter that can last me 15000km will solve my issue...

the amsoil website mention it was from USA, i have read a few articles that mention amsoil is the first company that develop synthetic oil, how true is it i not really sure, but at least i need to try first as most fully-syn oil won't harm my car, right...