Doing my homework for longer expeditions, and figuring out what I want to have on the vehicle as far as extra fuel is concerned. So far, I have seen about 10 mpg on trails I was running, so the 2 gallon Rotopax gives me just 20 extra miles and the 3 gallon, respectively, 30. Given the ~220 miles range of the full tank with this MPG, I'm wondering - are these 10-13% even worth the bother, or should I go for a bigger container right away?

PS: No long overlanding experience, all I ever did was day trips, though into some non-trivial places (7/10 according to FunTreks books).

 

I have a 3 gal Rotopax mounted on one of those BA Tents side ladder mounts (which I had to alter to accept the 3 gal tank - you just drill new holes about 1” to the right...).
https://newdefendermods.com/products...OdYzYb7C2GqDQu

Calculations ...
Offroad/trails I assume 10mpg on my truck = 3 gal = 30 miles range on trails
Forest Roads / on road I assume 18 mpg on my truck = 3 gal = 54 miles range on road

For my PNW day trip use case, is good enough to get me out of most problems I can get myself into.

I did not think a 2 gal rotopax, which is what that mount is designed for, was not enough so I copied a friend of mine and modified this holder to accept the 3 gal Rotopax instead I can supply pics / documentation if needed, of how I did it, super easy and looks great on the L663. The 3 gal rotopax does *not* stick out further than the ladder either, so it’s protected. Just like the 2 gal.

Now I don’t hit a trail without it. I almost ran out of gas this spring in the middle of nowhere in the Tillamook National Forest and it was quite stressful.

Note: on longer trips like when I went to Moab this year, I have a proper Wavian red Jerry Can 20L setup that goes up top on the rack in a Frontrunner jerry can holder that is slightly modified to accept Wavian cans - that’s another 5.3 gallons for another 53-95 miles of range. I can technically put 2 up there for double that but usually I have a water container up there as the 2nd one.

 

What modifications did you need to do to the Frontrunner jerry can holder to accept the 20L Wavian cans? Curious to know as I've been meaning to purchase the Frontrunner double jerry can holder to attach to the expedition roof rack. Thanks!

 

Basically the way the frontrunner double jerry can holder is designed, it can allow the Wavian (with more rounded edges) to slip out sideways. In fact, they will do so offroad. This is why the Frontrunner site says “not OK with Wavian cans”. I spoke to a Frontrunner product specialist about this actually on the phone this spring .

So you need to run a strap around the whole kit to hold it together. I use a Frontrunner Stratchit (stretchy) strap and it works brilliantly. There are 2 holes in the upper bracket that allow you to run the securing strap through. The stratchit is the way to go!

I also put a few hooks into the actual rack so it was super easy to disconnect. These pictures sort of tell the story. Zoomed in on explains.

I bought something from Powerful UK that goes into the roof rails, then another eye bolt that goes in the rack You can see how I did it. It’s super easy to take on and off and cinch down tightly. I went 10/10 in Moab with this setup and no issues. There is something that happens (a minor clearance issue) with the Wavian caps on the front where they have to be rotated in a certain orientation to clear the metal bracket on the front, but easily do-able.

 

Ping westcoastoffroaders.com. They should be close to you in the PNW. A few months ago they imported several of the LongRanger fuel tanks (Link) for the L663. Perhaps they still have some. That WILL solve your fuel problems. If you still are experiencing challenges after getting one of those, you need to star in the next Mad Max film.....

EDIT: Oops, your profile says "southwest". Shipping for you.