A slight errata:
This doesn’t change anything about the science surrounding the oil tank box cover and how it could provide an aerodynamic advantage, but it does clarify the situation with how the oil system is pressurized. Dan pointed out my error some time ago in the comments section to that blog, but it took me this long to get confirmation and an explanation from someone with enough patience to wade through it with me.
Here’s a flow chart of the engine oil system. I incorrectly stated that the entire oil system was “pressurized”, but only part of it is pressurized. The top oil pump (which directs oil to the engine) puts the oil under pressure. The crankcase (bottom of the engine) is at a lower pressure than atmosphere thanks to the bottom oil pump. This makes perfect sense, because how would the oil get back to the oil tank if there wasn’t a pressure differential? The oil tank itself (and the overflow container, which is located in the trunk) are both at atmospheric pressure.
My oil tank expert wishes me to point out that I drew two oil pumps, but that it’s really just one oil pump with multiple stages. The top box represents the pressurizing stage and the bottom pump represents the scavenging stages. The scavenging stages are the ones that He also points out that there are multiple scavenge stages, which are the pump stages that bring the oil back to the oil tank. The problem was that it looked more confusing than helpful when I drew the diagram with a single oil pump.
Thanks to Dan for pointing this out, and for advancing my argument with my husband that the third garage at the new house would make a perfect home for an old stock car. Just so I don’t have to constantly bug people who are trying to get their cars ready for the next race.