Well, cars came out with power steering long ago. Stores sell power steering fluid. The advice is not to mix the two. Manufacturers recommend power steering fluid in their power steering systems. They don't advocate changing or mixing the two. I'm not getting why they just didn't design the system to use a known lubricant, such as transmission fluid or motor oil. What possible benefit could be had for designing a system that utilizes a completely differerant fluid? Yes, I get the difference between brake, motor and transmission fluid. Just curious about the power steering. I could see using hydraulic fluid, or transmission fluid, or even motor oil. I'm curious as how they came up with a "special" fluid that is recommended, and how it might be so different. BTW, Hyd. fluid has MUCH more "lubicity" than power steering fluid. Millions of people dump in whatever works when they are low. It's not a game changer. So why the difference? Why not make it a common fluid in the first place? That's all.