About 30 years ago I was in Aachen in Germany in a 3.0 Capri, a couple of days into the stay I noticed we seem to be getting through a lot more Petrol than usual. At a petrol station the person filling his car up behind me came over and started shouting at me in German ( I dont speak a word apart from being able to order beer) Any way he pointed to the underside of my car and there was a large puddle of petrol under the car.
After some investigation I found several holes probably rust perforation and of course near the botton of the tank, I purchase some Petro Patch or equivalent and tried to patch up the tank, as I did this the holes got bigger.
Plan B was a 5 gallon Jerry can purchased from a Hardware shop and some pipe. After a bit of work the Jerry can was supplying the engine.
The problems were we had no gauge and of course with only 5 gallons we ended up stopping about 7 or 8 times just to make sure we didnt run out of fuel.
In hindsight I should have purchased 2 Jerry cans but we got home and had some very odd looks pulling the boot open and putting the petrol in there, on one occasion I achieved nearly 30mpg.