That’ll be me showing me age again. I remember when some of me mates had to replace their fibreglass café racer tanks for aluminium.
Barney get your hands on a magnet, in our house we keeps 'em on the fridge door.
For everything else there’s Baglux
Petrol tanks are always better made with metal than plastic. The ethanol content in modern petrol deforms plastic petrol tanks, so they stop fitting in the frame and/or leak petrol. Don’t ask me how I know this…
That’s bollox most cars if not all now use plastic tanks
And they are ethanol proof
And as above previous comment they offer better crash protection are lighter and offer up better options on placement
i think the clue is the enormous structural difference between the vehicles in question 
the petrol tank in the car is located very far from the engine and doesnt get affected by the heath. you can figure out the rest by yourself, or you should change your username
What? It’s got nothing to do with the structure of the vehicle or the heat of the engine, it’s down to the plastic. In the same way as there’s different metals that are differently affected by different chemicals, there’s different plastics with different responses to ethanol (and petrol). Old fuel tanks that predate the recent fad for high-ethanol-content petrol are often made from a plastic that reacts easily with ethanol, modern ones are made with an awareness of this fad and use different plastics, specifically ones that aren’t damaged by modern petrol.
not to forget now engines can & do have plastic rockerboxs & sumps so both heat & chemicals are catered for
petrol tanks are not always located as far away from the engine they are located in a position to survive a crash most metal tanks were located as far away as possible from the engine so in the event of a crash they didn’t splash all there leaking petrol over an ignition source
Right, thanks all for the contributions. I think I am going to have to try it and see to get a conclusive answer. I’ll keep y’all posted.
Good call. 
So time enough, did the magnets do their work or is yer tank bag in a hedge somewhere?