I'm pretty sure my needle stays above F for much longer, but never noticed in detail....I know with my Maxima, from brand new, it could be above F 70 miles. That may not be accurate, but I liked it (made me feel better lol). Actually when you think about it, it's like it goes down 3 gal before the needle responds...

I wouldn't worry about it, maybe just keep an eye on it...

 

Stuck evap vent

 

 

It will do that sometimes if you top off the tank, the car sits for a day or two or an animal plugs the it up. My car did the same thing and I thought I had to replace my charcoal canister. Its fine and as you experienced will start functioning normally after a bit of drive time.

 

All good now.

 

This time I paid close attention....with my mpg at 19.x since filling up, my needle first moved down, from above F, at about 37 miles, implying almost 2 gal. used. When you think about it, the fuel gauge is the same be it a 22 gal tank or a 16.5 gal tank, so it would seem the needle moves less on a vehicle with a larger tank, unless of course the vehicles say uses 36% more fuel...my .02