If the car was driven to empty from full tank - running out of fuel - then filling it again, noting amount of fuel you put in the car - and driven to fail from lack of fuel - and it duplicated the same mpg twice - that would be a more accurate way to determine mpg. If you can repeat the same mpg "44 mpg" (10) times in a row, until every tank exhausts it's supply - then I'd think you might have something.

Running the car from a full tank, to stop-running because of fuel starvation, 2-3 times in a row, is the best way to know your car gets "44 mpg." If I recall correctly - the '99 has a 21.1 gallon fuel tank, so, each tank you should get at least 928.4 miles per tank. Naturally, if you fill to the neck each time, you might get almost 1,000 miles on each and every tank - if your car is really getting; "44 mpg."

I've clocked nearly every tank fill for 14 years, and 129K miles, with the identical car, and it has never returned better than 32 mpg reading - and that was a one-time event, in all those years and miles. I've never been able to duplicate 32 mpg even once, much less 37 or 40+ mpg in my '99.