As I stated earlier, it wasn't getting the supplies to North Africa as was popularly believed but, getting them to the front once they arrived. The following table shows this:

6/40 - 9/40 148,817 tons 0% lost. Italians begin operations in N. Africa

10/40 - 1/41 197,742 tons 3.9% lost. British begin interdicting sea lanes. First British counteroffensive.

2/41 - 6/41 447,815 tons 6.6% lost. First German/Italian air offensive against Malta. Germans begin operations in North Africa.

7/41 - 12/41 356,294 tons 26.8% lost. British begin major effort to interdict sea traffic. British counteroffensive against Rommel.

1/42 - 6/42 441,876 tons 6.2% lost. Germans start second Malta air offensive. Malta blockaded. German offensive in N. Africa.

7/42 - 12/42 337,409 tons 35.5% lost. British begin serious sea interdiction. Alamein counter offensive.

11/42 - 2/43 225,189 tons 21% lost. US lands in French territories. Major attempt to interdict Tunisian sea traffic.

3/43 - 4/43 81,532 tons 42% lost. Axis defeated in N. Africa major withdrawal attempted.

Now, this just covers the supply effort. Troop landings were generally far more successful with far less losses.
In any case, what this shows is that the majority of supplies did arrive in N. Africa. What is not shown is that the inefficency on land was the primary cause of problems, particularly with fuel and POL products.
As an example, it is roughly 300 miles from Tobruck to Alamein. It is about 1500 from Tripoli the major port of entry for most supplies. It took about 260 gallons of gasoline to deliver 1000 gallons from Tobruck and just over a gallon of gasoline to deliver a gallon from Tripoli. The round trip transit times were roughly 3 days for Tobruck and almost 2 weeks for Tripoli.
When you add in wastage and what not, using trucks to bring the supplies forward was a major drain on everything. Without a rail line or a nearby port Rommel's forces were receiving very little of what was sent, particularly in fuel supplies.
The Italian Navy did a good job of escorting convoys to and from N. Africa. Many of their destroyers clocking well over 100,000 miles at sea. It was Rommel and his staff that failed logistically, not the merchant ships and their Italian escorts bringing them to N. Africa.