Fuel Consumption Error?

Ok maybe im missing some fundemental piece of naval technology theopry or something, but i was under the impression that when a sub is submerged it runs off batteris and when its surfaced it runs of diesel engines (unless a snorkal is used of course).

So going by that information which i am sure is correct, i shouldnt be consuming ANY fuel while submerged, only using up my batteries. So why am i loosing fuel while submerged. Ive never seen a message telling me i was leaking fuel when this has happened so im confused. It means i have to run on batteries and cant surface at all if i want to move.

This has happened on several occaisions and it didnt ever bother me until the KLM mission 3 when i wanted to surface and run cos its faster. but i couldnt as i had no fuel.

Sounds like a bug. We'll put that on the list to address.