The Science of …Oil Tank Pressures

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.


  1. Nice follow up. I apologize for being argumentative. I’m really impressed that you didn’t just blow it off. Good luck with you garage acquisition!

  2. Hey Dan:

    No apologies needed. I appreciate people who feel strongly about getting things right! You obviously have a lot of expertise, so I will count on you to keep me honest in the future.

  3. There is way that you can stop engine engine depression by adding a small load vacuum pump with screen in sump to pull vacuum to atmosphere. Engine depression big problem in F1 engines. You can also do it the old fashion way by having bleed lines that recircilate back to the system.

    Engine oil purification can save world from going hybrid crazy and going green. I am going to DEI right now for funding it doesnt have racing application but has real world application for consumers to buy at Sears and Home Depots across the country.

  4. engine oil purification by centrifugal force before qualifying would help oil system drastically. I have talked to Steve Wilson of RCR since 2005 about it.teams to find a way to heat up coolant just below boiling
    200 degrees before qualifying

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