I've got a long ranger on mine and frankly, I'm not impressed. They are supposed to be bespoke to the vehicle, but didn't come with the required fittings to mount it, and it's not properly baffled so the fuel slops about and could lead to fuel starvation problems going up hill as a result. also the shape of it, being square at the front rather than profiled and hanging low meant I had to get a bash plate made up to protect it.

Given the cost if I did it again I would get someone like allytanks to make a proper bespoke design, which would cost about the same and fit better.
It only gives me an extra 65 litres, so about the same as 3 jerrycans which is what I generally carry. It's much better in a tank. cans would usually go on the roof, so a lot of weight up top wheras a tank is low and central to the vehicle. and in a tank there are no problems with duties crossing borders. I wouldn't want to carry more than 3 cans on the roof so now, if I really need it then I could carry a further 60 litres on the roof, giving me 125litres extra, but I've never needed that much.

The tank is a simple gravity feed, but it takes about 30 minutes to flow from the main tank to fill the aux so it makes brimming the tanks on a single fill impossible.

Also, if I hole the tank I lose all my fuel. Personally I would avoid all the fancy electronic tricky of solenoids, more to go wrong, and have a simple manual tap so if you whole your lower tank you can isolate it from the other tank so you don't lose all your fuel before repainting it. Ideally, if I really need more range I'll get a bespoke tank to replace the main tank and spare wheel and mount the spare ona carrier. That would give me about a thousand mile range which is kind of the target I have always had in my head.

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1990 Landcruiser H60. Full rebuild completed 2014