will a full oil drum float

To sink, a drum with a volume of 55 gallons must weigh more than 458 lb (the mass of 55 gallons of fresh water at ambient conditions). If it weighs less than that, it will float. (You can of course repeat the calculation for salt water if you prefer.)
Now how heavy are the drums, empty... 80 lb has been suggested. Then the oil can weigh no more than 378 lb. If the drum is full with 55 gallons, the oil can weigh no more than 6.87 lb/gal, or a specific gravity of 0.82.
This will vary slightly with temperature, of course.
Thus, 40 API crude oil (SG 0.825) would be borderline, but any higher grade (48 API, for instance, at 0.790) would float. #2 diesel at 0.820 would only just make it in cold weather, probably would sink if the lake is warm. Gasoline at 0.711 to 0.737 would float.
But drums are never quite full, leaving you a slight margin for error if you misjudge the lake temperature or something.

 

Marshmat,

I think approx. 80lbs. for an empty 55gal. drum is a little high.

Though never having wieghed one, I have moved & carried empty burn barrels and the like that we use 55gal. drums for. Just guessing, I'd say they go less than 65lbs. With the cut-out lid I still think they would be under 70lb.

The water we floated the drums I speak of above was under 40'F, while the diesel would have been around 50-55'F.

These drums were most likely not fiiled right to the brim.

Take care.

TGoz

 

Actually, the avgas used in Trieste (DSV1) and when rebuilt as Trieste II (DSV1), and FNRS-2/FNRS-3, and Archimede; is more compressible that water (which is also compressible at 10km depth) and also loses buoyancy at depth because of increase in density due to the lower temperature at depth. The compression of the gas was so large that the big worry was not the temperature loss on diving, but the temperature loss on ascent. The adiabatic expansion on ascent wouild cause the gas to grow even colder which had the possibility of causing a freeze plug in the seal water as pressure was released (only the great pressure at depth keeps the saltwater from freezing). This could cause the float to rupture ( and thereby the loss of the bathyscaph) as the ascent continued. Temperature of the float gas is very closely monitored for this reason.