We race HQs up at wanneroo, and while we were able to get Shell Optimax it was far superior to BP Ultimate.
The old Optimax was the Shell V-Power 100R, which apparently is not being made anymore. The current Shell V-Power is not the same as Optimax was.
When we first could no longer get Optimax, we changed to Caltex Vortex as word of mouth was such that it would perform better on the track.
After racing a few meetings we had a spare day on the dyno, so we had the cars tank full of Vortex 98 and took a test tin of BP Ultimate that we could easily swap the connection from the tank to the test tin at the source to the fuel pump.
Without any adjustment to the carby or
distributor we ran the motor for a while to empty out the residual Vortex. On the first run up on the dyno the BP Ultimate was something like 2hp higher than Vortex pretty much all the way up the curve. Each run after was higher and higher. This was 2 years ago, but from memory we finished about 5-7hp higher with the Ultimate than we got with the Vortex without changing anything.
On a modern car this would likely result in a much higher gain.
I dont work for any fuel companies, and stand to gain nothing by giving you this information. This is just my experience with the products