There's speculation (and word on the street) that what you're pumping into your car may not actually have been produced by the company on the sign. Apparently they regularly purchase fuel from each other, be it for supply and demand ("Hi, Shell? It's BP. We've run out of 98 and need another 5000L. Hook a fella up, will ya?"), or cost saving on transport, etc (it's freaking expensive to ship fuel from Sydney to Perth, cheaper to buy it from BP). Whether the additives are the same in Ultimate as Vortex as V-Power and so on, or whether they each add their own blend of additives, I don't know.