is there a standard factory fit size for them i.e 250 lts, 350lts etc, reason i ask is when the low fuel warning light comes on when you get to the red , it normally takes 260/ 270 lts to fill our trucks back up.
one of our lot thinks the tanks are 350lts, i always assumed 300 lts[ 40 ish lts left in when you get to the red] , could it be 80 lts , sounds a lot to me but i just wondered.
dont normally let it get to the red but it does happen and im always wondering will i get to next garage but if there is 80 ish lts left in when yo get to red its not such a panic . thanks
ady1 Give it the road test then you will know for sure. 
thanks harry but i think ive given it a few too many roads tests lately 
ady1:
thanks harry but i think ive given it a few too many roads tests lately
I saw a truck with large tanks run out of diesel (44t!) just off the pumps by about 10 meters. He turned it over on the starter in gear to get it to the pumps before he stuck 800 litres of diesel in. Took him a while to restart the engines (I was behind him and boxed in 
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ady1:
is there a standard factory fit size for them
Short answer:
No.
Longer answer:
Fuel meter should be calibrated such way that you don’t ran out of fuel even when driving to ferry (or steep hill, etc) with “empty” tank. This means that when gauge shows empty tank you should still have some amount of fuel in tanks. I wouldn’t trust too much into this, but in general I think you are quite safe to go as long as long as gauge shows even a little bit of fuel in tanks.
If in doubt, ‘Dip’ the tank(s) 
The trouble with large tanks is that you forget to fill them up,on UK ,that is.