I have Fabia 2 without computer and of course i can not see fuel consumption...

In this case i am thinking to buy  "OBDSPACE P10" or "Vgate iCar2 ELM327"...should i see the instant fuel consumption, fuel consumption..??

Fill it up, set the trip counter, drive around as normal. Next time you fill up, divide the distance you drove by the amount of fuel you put in. 

Fill it up, set the trip counter, drive around as normal. Next time you fill up, divide the distance you drove by the amount of fuel you put in. 

Yes..i did it a few times.. I know. 

While my Greenline has a trip computer, I tried using Torque on my Android phone and a Bluetooth OBD2 adaptor to review consumption. While it showed a consumption the value was constantly changing so I can only assume that the sample rate is much higher than the on-board display.

It is most likely showing "instant" consumption which will be all over the place as you drive, you need an "average" consumption as well.

 Just plugged the Bluetooth OBD into my daughters 60 plate Polo 1.2, which does not have an on-board computer, and Torque on my Android phone gives fuel economy with a much slower refresh rate, therefore the readings are quite stable and easier to read. It also has an option for average consumption, and lots more such as voltage which is handy if you think you have battery/alternator issues.

Super!!!

I just ordered a vgate obd2.

Shall i see the instant fuel consumption? Do you see that?

It does on the Polo, can't comment on Fabia 2 as my Fabia Greenline has computer and Torque gave dubious readings - refresh rate too quick.

my torque app increases the reading of fuel consumption when i let the car roll in gear where the car computer decreases it. I have along hill on the motorway near home and i can start at the top of the hill with 60mpg, without even touching the throttle i let it roll for about 1mile in gear and when i get at the bottom of the hill the app reads and average of 20mpg .  I don't know how to set it correctly, i just wanted to compare it with the car's reading.