On my mazda 6 diesel the fuel gauge seems to registering say half a tank of fuel
but as i drive along the gauge moves down very slowly but when im on a quarter
of a tank of fuel the fuel computer reads 155 miles left has any one had this happen to them

 

I just purchased an 06 Sportwagon and I've noticed a similar issue. When I fill the tank, the gauge only shows 3/4 full. Seems to drop quickly to 1/2 tank. But since I don't have a DTE option, I'm not sure, but it seems like they gauge is not calibrated correctly.

 

My wifes car is an 05 Mazda 6 and i had to change the fuel pump awhile back. It was sooo easy to change because its under the back seat, under the acces plate.Maybe the sending unit is bad. If you take the pump out, have a pan or a bucket handy because the fuel pump has about half a quart of fuel in it so when you pull it out,gas can get everywhere if you tip it.

 

The fuel gauge should not be used as an exact measurement of how much fuel your car has in the tank. It should only be used as a reference. It will move slightly when on inclines/declines.. maybe that helps..