Incorrect fuel readings

robma2002

I have a 2007 Nissan qashqai and when I top up say £30 it shows that I have 308 miles to drive.
When I drive from the fuel station to home which is 1.5miles, it indicates that I have like 285-290 miles left and it continues that trend until it drops to a point of having the fuel warning light on.
I have tried to Google the issue but am getting various reasons for the fault. Has anyone experienced this and how did they fix the issue. 
Many thanks in advance 
Robert. 

The_Fat_Controller

What ACTUAL MPG are you getting ?
When the fuel warning light comes on, how much fuel can you actually add when you brim the tank ?

AdrianC

Range is usually calculated as the average consumption over the last few minutes of engine running.

£30 at £1.25 would be 24 litres. 308 miles from 24 litres would be 68mpg.

Calculating economy should be done over several tanks, ideally brim-to-brim.

lopsyfa

Above is your answer.

The mpg you get then depends on several things such as the weather, your driving style, the route (driving uphill will use more fuel, motorway Vs local) etc.

So if you manage 60% of the mpg stated above, that is still about 40.8mpg which is not bad for this time of the year depending on the other factors. I will say there is no fault with the car and don't look for one as there are several garage that will gladly collect your money to look for non-existent faults.

But if you are getting less than 30% of the mpg, then it is an entirely different matter.