I also owned a 2001 vitz since last year ! Bro, this gen of vitz is very strong and tough & rough ride ! You can do anything with it, but it can't put its hands down, until its last breath. I am using havoline 20w-50 formula all the time, since I owned the car ! About gear oil, go for original Toyota ATF T-IV (T-4). It is packed in a 1-litre tin-pack. You need 3 litres of new ATF, after draining its old ATF completely ! Its 1-litre pack costs 800-850, I think so !