As a lifelong mechanic I say use the fluids the manufacturer recommends for the specific vehicle or its components, for whatever that's worth.
If your engine requires regular fuel, use regular fuel. You're throwing money away and reducing efficiency, especially in today's hi-tech IC engines, if you use other than that specified by the engineers who, actually, do try to improve the automotive industry, despite the many, many times I cursed their design idiocies.
Like having to remove the steering column from a car to replace the starter. lol