Hi! I tried searching to see if this has already been posted about and didn't find anything, but I apologize if it has, I'm not very knowledgeable when it comes to cars.
I've had a lot of trouble with low air pressure in my tires, which may be a problem in itself - I got new tires but the front left is low a couple months later, the same tire that was often low before, so I don't know if there's something up with my wheel or whatever, but that's not even what this post is mainly about. I have had to fill the tire a fair amount and it's always really tricky to access the valve, as it is right up against the hub cap. I don't know if this is a problem with the hubcap being a bad fit for the wheel, or the valve stem not being long enough, or what. I am not sure what the best thing is to do, if I should get one of those valve extender things, or if there's something up with the hubcap, or something else. Until I figure out why the same tire keeps being low, I'd like to at least be able to fill it up without the guy at the gas station having to remove the hubcap for me while I feel like an idiot

 

For one thing, the hubcap could be installed wrong to begin with... there's a slot in the plastic cover to make room for the valve stem. And the inner locking ring also has a notched area to hook around the valve stem.

Secondly, removing the hubcap is nothing more than pulling/prying it off... it's a clip on cap.

If your tires are leaking air, there could be a bad seal between the tire and the steel.

 

Ditto what Goobers said.

I will add that the valve stem length is fixed because the stem is part of the TPMS sensor. Your valve stems should be the same length as all other Fit's. They aren't long, but are long enough.

You definitely should not be loosing air. A simple dunk test is a quick way to find the leak.

Another possibility is that someone is messing with your car.

 

I have had several air leaks on different cars:
1.) CIVIC with OEM aluminum wheels had road salt corrosion right where the bead of the tire would seal. I broke the bead and used fine steel wool to polish out the "chalky" area. That didn't work and had to eventually buy an aftermarket replica wheel. Now perfect.
2.) I tried to loosen the threaded sleeve on the TPMS sensor so I could add some grease around the O-Ring / wheel rim to seal it better. That didn't work because the road salt had corroded everything together and the stem snapped = rapid deflation.
3.) Not sure why but the TPMS broke away from its stem and you hear it sliding around inside the tire / rim. I had taken the tire in because of a slow leak but I think they busted the TPMS sensor with their tire machine.

I like the TPMS concept but not its execution.