It should update whenever you add or edit a fuel-up. If you're not seeing an updated version you might have the image stored locally in your cache. Even though we tell browsers not to cache these images in as many ways as possible, some browsers and networks are still aggressive about caching.
Go to the page where you're seeing the "old" image, and try a Ctrl + Shift + R. This will bypass the local cache in most browsers. If that doesn't work, take a look at
these instructions for your specific browser.
No luck then? Try
editing your latest fuel-up and give it another shot.