Yes okay i do agree but you forget what kind of cargo a tanker had.
Did you ever hold a burning match to a drum of benzin?

I can remember in my youthtime when i saw wwII documentary on tv that a wolfpack attacked a convoy and that tankers were burning and / or exploding very well.

I have never read about it on this forum that people know about
very dangerous cargo a tanker can/could consist. Everybody thinks that
a tanker in the game transports milk or so.

Only how difficult it is to sink a tanker in the game by compartments.

Man oh man what is this for kind of speaking.

For example, the Jave (photo hereunder) sunk within 15 minutes by one japanese torpedo.
How? It had just loaded his seamines under deck.

Tanker cargo could include any of the following and more:

Fuel Oil
Aviation Fuel
Jet Fuel
Crude Oil
Diesel
Gasoline
Sea Water ballast
Fresh Water Ballast
Machine or Lubricating oil (not explosively combustible)

Remember Fuel vapor is what really burns - i have seen a lit match submerged into a jar of gasoline - which extinguished the match just as if it were submerged into water. but when you begin to place a cap over the jar with a small hole and repeat the process you get a jet shooting out the hole.

If you slam a ww2 era torpedo into the side of a tanker the oil contents are not likely to just explode with catastrophic force sinking the whole ship in seconds. The compartment will flood to an extent, oil will spill out to an extent. Naval Architects design ships with this sort of event in mind.

if you REALLY want to kill a tanker catch him under the following conditions

1. Moving slowly
2. Calm or no wind
3. Calm sea
4. Torpedo the ship once to cause a breach
5. Torpedo the ship a second time to detonate the contents

here is why this works:

A slow moving tanker in calm wind and calm sea's has a hard time getting rid of exposed fuel and oil vapor. If you torpedo him, massive amounts of vapor will leave the ship rapidly enveloping the ship in a cloud of explosive gasses. All it takes is one tiny spark to take her out... thats where the second torpedo comes in :)

set one torpedo to magnetic detonation under the keel in a spot just forward of the wheel house. send a second torpedo with impact detonation at about 4 meters running depth. This will guarantee you a sinking and will almost always result in the tanker splitting in half.

And we all forget the SS Ohio

http://en.wikipedia.org/wiki/SS_Ohio

There was a tanker that didnt sink despite being torpedoed\bombed and having a Ge aircraft crash onto the deck
Was a bit of a mess but no grand explosion

Sometimes tankers explode sometimes not

The mission editor has 3 cargo loadouts for tankers
Only 1 is fuel
So there is a chance the ship wont be carrying anything volatile
Torpedo that and you wont ever get a fireball

Mind you one of the other loadouts is ammo so thats about as explosive as you can get

My favorite is the San Demetrio: the tanker that not only didn't sink, she came back to rescue her own crew!
http://en.wikipedia.org/wiki/SS_San_Demetrio