I have a total of 180lt in a 110 wagon spread across 3 tanks, main, rear quarter and sill. I intend to keep the vehicle a very long time and every time I drive past a station selling at $3/lt I save at least $100, do that 10 or 20 times which over the life of the vehicle and the tanks will pay for themselves which will keep the bean counters happy.
I also rely on the range which is why I invested in them but also consider where you are going to store them, 120lt of fuel or water on the roof of the vehicle is madness IMHO. Weight on any extremes of the vehicle is not great but especially high up, like when you see those trucks with the water tubes on the roof racks.
I do wonder though about 300lt in a 90? that seems like a lot of weight and room Sue you must be planning some pretty remote trips.

