All the radial engines that I worked on were dry sump engines. On the R-4360-59B engines that I worked on in my Air Force KC
/C-97 days, each engine had a 27 gallon engine oil tank mounted in the QEC just behind the engine, (the Quick Engine Change is where the engine is mounted too and has all the hoses and plumbing and all the other accessories that are not directly mounted on the engine, the QEC is what is bolted to the airframe, the engine is mounted to the QEC). The engine oil tank shared the same outer housing as the turbocharger oil tank, which held if I remember correctly 3 gallons of lighter turbo oil. If the FE
over serviced the engine oil tank and the turbo oil tank was not full of oil, the turbo oil tank would collapse.
On the FE
’s panel was an engine oil quantity gauge with a rotary switch for each engine, in the lower forward cargo compartment was a built in 55 gallon oil tank and the FE
could top off the individual engine oil tanks in flight. A low time R-4360 could normally use 1 to 2 gallons and hour of oil, older engines could use over 3 gallons an hour.
The belly oil tank was serviceable in flight and on long trips extra oil was carried on board and the belly tank was often serviced in flight. Some units even modified their airplanes and installed a 55 gallon drum with an electric pump so they could easily top off the belly tank.
/C-97 had over 10 hours range, easily flew from the west coast to Hawaii, so on a long flight sometimes oil was the limiting factor, if the airplane had 4 higher time engines they had to make sure they had enough extra oil on board.
On our base, we had a 500 gallon oil truck to service the oil tanks on the airplanes, the engines used SAE 50, 100 weight oil so in the cold winter days engine pre-heating was required. The oil truck was filled from 55 gallon oil drums lifted up using a fork lift and in the winter the oil was like molasses.
Before engine start we would walk the prop through in the direction of rotation 12 blades to make sure none of the lower cylinders had any hydraulic lock. On cold winter days it sometimes took 2 people to walk the prop through, fortunately the engines were low enough to the ground to no ladders were needed.
One funny story, I was on board a flight as an additional crew member when we flew to a civilian airport in Florida to pick up a high level General. The belly oil tank needed to be topped off so we asked the lineman of they had gallon cans of oil, we needed 55 gallons. He said that all they carried was quart cans, so he came back with 10 cases of engine oil, 24 cans to a case and in those days using an oil spout topped the oil tank, one can at a time. After emptying almost 200 cans he thought he was done, then the FE
topped off the engine oil tanks with the internal pumping system and used up almost half the oil in the belly tank. The FE
then told the lineman he needed to get another 5 cases and the look on this poor lineman’s face was incredible. The FE
then told the lineman he was kidding, we had enough oil to get back to our home base.
Unfortunately for the lineman, this oil and the fuel was charged to a military credit card so there was no way we could give him a tip, which he so well deserved.