There are a couple different ways you could do it.
1.) You can set a primary vehicle in your profile.
Go here and set a Primary Vehicle (it's the 3rd option from the top). That vehicle will come up when you go to fuel-up.
2.) Go to the profile of the vehicle you want to fuel-up. Click the red "Add a fuel-up" button at the top of the page. You'll go to the fuel-up page with that vehicle selected. Bookmark that page in your browser and that vehicle will come up every time you use that bookmark.
3.) Use
fuel-up importing. If you have more than three fuel-ups or so it might be worth jotting them down in a text file and using the import feature instead of entering them manually.
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