Dear nawaz bhai,
It is important to know that when your car was sent on periodic inspection in japan there must be maintenance card hanging some where near by your car steering.
Then try to change oil, air filter, oil filter, and spark plug in one go. Recommended oil grade is 0w20 (any brand will do) and if you can't find this grade in market then go for 5w30 grade. Everything mentioned above are available at auto care pharmacy, malik autos. Make sure you buy the right stuff particularly plugs for 1krfe engine. It will be better to if you will match the stuff you buy from market with the installed stuff.
Oil change will cost you 100 to 150 which includes the replacement of air filter and oil filter. While spark plugs replacement make cost you 150 to 200.
You don't need to take your passo to Toyota as they don't change anything but charge more even some time they pour wrong grade oil which spoils your mileage so make simple just give car for complete wash any service station and ask them to avoid using water dropping cloth on doorand window controllers.
If you are looking for good Japanese car mechanic then you can visit asghar autos where Ali is the person who does brilliant work of jdms.
Please also check that you are driving your passo on econo mode green light on while driving and keeping your foot light.
Hoyee this will make the clear difference between your past and post experience. If there is anything I can do, please feel free to write or contact me here.