I have ford feista 1.4 mk7 

When I put it full tank

it run 7 days 

It doesn’t also run 300 to 400 a full tank

so can someone tell me solution 

please ?

Not sure what you're asking here? Are you saying when you fill the car up it lasts you for 7 days? And you don't get 300 to 400 miles out of a full tank? 

If it's an mpg question, you need to measure it much more accurately than that. Fill up the tank, zero your tripmeter (or note your mileage). Then, when you next fill up, divide the number of miles covered by the number of litres you put in to bring it back to full, then multiply by 4.54609 to convert to mpg.

You don't mention if It's manual or auto, but It wasn't a particularly economical car when new and if you're driving in a city area you're unlikely to get very good economy.

 

 

 

 

I put full tank and reset the mile 0

then it give me 260 miles 

16 minutes ago, Mohaa said:

I put full tank and reset the mile 0

then it give me 260 miles 

I assume that was the range to empty shown in the trip computer, rather than you saying you drove 260 miles and ran out of petrol?

If so, that's the estimated range based on your recent usage and driving style. You need to complete the exercise by actually driving a reasonable distance, for example, 200 miles, then filling the car again, and completing the calculation mentioned in my earlier post, to give you an accurate actual mpg figure. 

It would be helpful for anyone commenting to know how and where you use the car. If you are doing short journeys in low gears and heavy traffic, for instance, your estimated range and actual mpg will not be good.