Many long range aircraft had aux oil tanks for transfer to the engines. The L-1049 Super Connie had a 67-gallon bag tank in the port wing root - The WV-2/EC-121 radar Connies, because of additional fuel, had a second aux oil tank in the starboard wing root. These tanks and lines had electric heat so the stuff would flow when cold. The Douglas types with aux oil thinned it with gasoline so it would flow.
Some engines types were notorious oil leakers - the R-3350 BA series on the L-049/L149 Connies was one such, probably the worst engine ever on an airliner. Had old type hose and clamp seals on the pushrod housings (36 of them) which leaked all the time. Lots of connections for rocker box drains that leaked. In fact if you saw a really clean area on a BA engine, you immediately suspected an fuel injection line leak. Later models (BD, CA, DA, EA) were much better so far as leakage goes.