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.
Should you change oil as often as every 3,000 miles then? Unless you want to see your mechanic every two months, a 3,000-mile oil change interval is another extreme. If you check your oil 3,000 miles after your last oil change, chances are it will still be pretty clean. Unless you race your car daily, even mineral oil can last longer than 3,000 miles. Most car manufacturers recommend 3,750 to 10,000-mile oil change intervals.