In the 50's we used a thing called a sludge pump. Cheap ones were marketed by Fram, Alemite sold an expensive chrome one. It is nothing more then a cylinder with a plunger to create a vacuum. At one time we had so many oil changes that we rigged one out of a tank like an old truck saddle tank. We would pull the tank down with vacuum and suck the oil out into the tank. When the tank got heavy, we would apply about 10 psi air to it and squirt the oil out. I just looked on ebay and someone has an alemite suction gun with a starting bid of $6.
