Blood is mostly made up of water, as are our organs and muscles. To read specifically about edema, swelling caused by fluid retention where excess fluid is trapped in the body's tissues, see our article Edema: Causes, Symptoms and Treatments.
If you use the Amsoil Ea15K01 and the ASM oil (For 3rd gen Prius), then you can safely go 15,000 miles between oil changes. I drive 25,000 miles per year in my Prius. Amsoil backs up their products by a written warranty.
In UK it seems to be most often recommended that oil and oil filter get changed every 10,000 miles or every 12 months, with optional changes between those times. Depending on what car you have, it's possible for even a total noobie to do interim oil and filter servicing, quickly and with a lot of ease.