My Dad says impossible because of a flapper. Filled up in a rural area. Parked in a very safe rural area. Came back to gas door open and screw cap hanging down. My Dad spoke to the local mechanic who said to look under my car–that people only steal gas under the car because of the flapper. I am not crazy.
How much gas did they take? Does the tank currently hold gas? Because of anti-siphon flappers, thieves will drill a hole in the tank from underneath to get the gas. But it sounds like they didn’t do that, otherwise the tank would still be leaking when fresh gas was added. Visibly leaking. I’d be worried that something was put in the tank if little or no fuel is missing. If there is some fuel missing, they may have found a way around this flapper and still siphoned the gas. I think anything more than 5 gallons means multiple gas cans or a custom rig, meaning more of a profession gas thief than a kid swiping free fuel.
It is possible to get around the anti-rollover valve by using a small enough hose. The thief would have to spend quite a bit of time waiting to get gas out with a small hose.
My 98 Pathfinder has a flapper also…And one day it froze shut…I was able to open it with a small flat screwdriver. Unfortunately I did scratch the paint…But the truck had over 300k miles so it didn’t bother me that much.
I think that you are talking about the flapper at the top of the fuel fill tube, the one that you push open with the nozzle. I assumed that the OP was talking about the anti-rollover valve at the bottom of the fill tube that you can’t see.
The flapper at the top is no deterrent to theft since you can push it open with your finger.
Do you have any teenagers in the family?
Here’s my theory. Someone takes it on a joyride, burns however much gas and instead of replacing it leaves the gas cap open so you will conclude someone siphoned it out.