Fuel requirements

What I really want to know is fuel available en-route. When I read the trek notes someone may have been carrying 190 lts and only used 150 lts so it indicates they need not have filled up on the way. Another set of figures can be the reverse. Carried 150 lts and used 190 lts. The latter indicates they must have filled up on the way, but where? The first example indicates that if we have 120 lts in our tank(s) we need to carry 70 lts of fuel extra in cans when in fact there might be fuel available on the way.

Sorry

I would need to know which trips you want to take and then maybe I will be able to help

Richard