My 2008 S80 when I travel longer distance of over 120 miles, the car acts as though it is running out of gas when it has 3/4 of a tank of gas. Once I top off the gas it runs fine for about 30 miles before doing this again and again I top off the gas and it does this over and over again after 30 miles. But it doesn't do this on my everyday commute.
What could be my problem?

 

Do you let the gas pump click off when it's full, or do you 'round up' to the next dollar after the gas pump clicks?

 

I round up