Quote Originally Posted by chuaed View Post
pwede rin mag install ng air-fuel ratio meter...

Air
True. But if your car does not have a factory installed oxygen sensor, it is going to get expensive. You will need to buy a air/fuel ratio meter with oxygen sensor and find a place to have the oxygen sensor installed properly and another place to install the meter and wire it up. (yup I have done that already). If your car does have a factory installed oxygen sensor, if its a single wire type, readings from it may be inaccurate if it is in the wind path of the radiator fans.

After all that, the A/F meter is only good for telling you if your engine is running properly or to help you tune your engine on the go. It will not tell you if your driving habits result in good, average or poor fuel economy.