What is Reddit's opinion of 2.5 Gallon Fuel Storage Tank Gas Container Can Cap Replacement for Jeep SUV ATV(1 Piece) USA Warehouse (Yellow-2.5Gallon)?

From 3.5 billion Reddit comments

If you look at modern passenger car fuel tanks you'll see that they often have very odd shapes because they're configured to fit tight, irregular spaces. As such, it's often difficult to complement or expand them in any way, unlike trucks or antique cars.

Along with following u/ScottDougJohnson's advice posted in this thread, you could carry fuel in an approved container in your trunk if you have an extreme use case. In addition to traditionally shaped containers, there are interesting flat designs (often used by off-roaders) that might stow better in your trunk.

If you're willing to pony up some money, you could reach out to a custom fabricator to see what your options are. I've never looked into this personally as I've never felt compelled to expand the tank capacity on any vehicle I've owned, but some quick googling reveals the following:

• https://www.tanksinc.com/
• http://www.boydwelding.com/

This was my Google search. Hope this helps and good luck!