As I have decided to stop sending my car to Toyota Service Center, I had the liberty to choose after market products particularly for engine and transmission oil. My transmission was dued for change, as it had ran for more than 50,000km since the last change.
I did some research and eventually bumped into AMSOIL products. The thing that caught my attention about this company is that they offer products with extended oil change. Their meaning of extended, is really extended. According to their product description, their Universal ATF can last up to 80,000km under servere service.
I felt a car transmission system is a very important component. If it fails, it is going to be very sticky and costly. Therefore I rather not compromise on the choice of transmission oil to use. 
AMSOIL Universal ATF seemed a good choice, after reading all the reviews and feedback from road users. Furthermore AMSOIL products is very reasonably priced, and since it last twice longer than Toyota's ATF oil, I decided to give it a shot. Apart from its distinct durability, it can resist oxidation at high temperature. Very suitable for Malaysia's driving condition.
AMSOIL Universal ATF seemed a good choice, after reading all the reviews and feedback from road users. Furthermore AMSOIL products is very reasonably priced, and since it last twice longer than Toyota's ATF oil, I decided to give it a shot. Apart from its distinct durability, it can resist oxidation at high temperature. Very suitable for Malaysia's driving condition.I drained the oil by removing the oil sump and also the filter. Fortunately I purchased 5 bottles (each bottle contains 1 litre), because after draining, it required about 4.5 litres. During the oil change, I noticed there were a lot of metal wear collected at the oil sump. I suppose it was considered as normal metal wear occured over the past 180,000km of driving. I would expect with AMSOIL ATF oil, it should deliver better protection against wear. Though it performs better, I was advised to go for next oil change after 40,000km as this changed doesn't replaced the old oil fully yet. It probably replaced about 60% at the most. I will need to go for next 2 oil changes to be sure that it has 90% or more of AMSOIL ATF in my car's transmission.
After this oil change, I noticed the gear changing especially at high speed was much smoother. Even when it drops down one gear shift for acceleration or climbing, the shift down drag was very minimal. However I still noticed the harsh noise when running on 1st gear. Not sure whether the harsh noise was coming from my engine running at higher RPM or it was from the wear of my transmission at 1st gear. I should be able to confirm this when I go for next engine oil change. There is possibility that it came from my engine, as it had already ran for about 11,000km since last oil change.
Anyway there shouldn't be any compatibility issue, as AMSOIL claimed that they comply to Toyota type IV and also read a number of Toyota owners using AMSOIL ATF gave good reviews. However there was one owner who had problems with AMSOIL ATF. It was then later discovered it wasn't because of oil incompatibility, the problem was due to the old oil was not flushed properly, therefore there was diluted mixed and plus the contaminants that came along with the old oil.
I can only confirm the effectiveness of AMSOIL ATF at the next oil change (that would probably be next year), upon examining the oil sump. After reading all the reviews and good things about AMSOIL being a reputable motor oil company, I believe I won't be dissapointed with this product.
