Would not work so well on my rig less In installed a door over the cap (Whcih I'd like to do some day and likely will.
I have another method that works though.. I stick the cap in my pocket, same one with the keys to the ignition and thus, always remember it.
HINT to thoe who burn gasoline like I do and who also shop Wall-mart
If you go into the store and buy a gift card (3 bucks, one time purchase, I got 2 of 'em free however, one due to an in-store refund, one .. Well. I just found it)
Then you can go to the customer service desk or any register (manned) and hand them the card and say 100 bucks (or however much) and tell them "Fill 'er up" and they will.
Now go to the Murphy's in the corner of the lot and stick the card in the pump and watch the price go down Current discount is 10 cents per gallon.
Save the card, next time you can re-use it.
Some wal-marts and cards you can even do it at the machine (Auto-teller) no need for human assistance.
Home is where I park it!