ljadw wrote:what would use the Bismarck/Roma :fuel oil,or diesel ?
Bunker oil.
Diesel was used in the German Navy only by submarines & the Deutschland class (for the ocean-going ships, a good number of coastal craft were diesel-powered)
ljadw wrote:The Italian navy was able to do the essential things,their main mission :to protect the convoys to NA,thus,why should they have a shortage on oil ? ....
I'm also in disagreement with this sentence wrt the main mission of the Italian Navy.
Yes they were able to achieve their "minimum" mission - preventing the Royal Navy to gain control of the central basin of the Med. But they were unable to fulfill their "maximum" mission : gaining control of the central Med.
This area remained contested until the landings in Sicily, whereas, with a more active Italian Fleet it could have become a no-go area for the Mediterranean Fleet.
Now, it's not only the oil shortage that played a role here. The italian high command at also something to do with it - at least in the first year of the war. Because from mid 42 at the latest there was simply no more oil resources to speak of for the heavy units.
Note also that an important factor in the cancellation of C3/Herkules is the problem to find how to fuel all the ships which would have been involved.
The controm of the Mediterranean did not depend on the RM,but on the advance of the ground forces in NA:if Rommel had arrived at the canal,the Axis would have the control of almost the whole Mediterranean .
You look at the problem the wrong way. Which was also the case of Rommel and many a general by that time.
But the point is that it's the control of the Mediterranean which was a mandatroy prerequisite of a capture of the Suez Canal by Rommel. Not the other way round.
Rommel needed large supplies to reach the Canal, supplies which could only come by sea. He also needed coastal shipping to relieve the congestion of the coastal road.
And to have a free flow of supplies through a sea/ocean, you need control of said sea.
Actually, the situation by mid-42 was the perfect illustration that reaching Suez to get supplies flowing was the wrong way to do.
ljadw wrote:Until there are proofs that the main mission of the RM and the Italian merchant fleet

(always forgotten),which was the convoys to NA,was seriously suffering from oil shortage,the claim that there was an oil shortage remains unproved.
Logically unsound, especially as the main mission of the Italian Battle Fleet was definitely not convoying.
And there are many an illustrations (or "proof" if you want) of those shortages. I already mentionned that after mid-1942 the RM retained only one full oil load for its main battle fleet. It's also well-known that the battleships did not sortie against Pedestal because thay had to empty their bunkers to fill the cruiser's bunkers. And as said aboce, the cancellation of C3/Herkules owed a good deal to the lack of oil.