Opticrap
NEVER use Optimax in a a Bravo/a. The VVT engine adjusts to reduce the mixture to get the right combination and therefore reduces power accordingly and the non VVT engines cannot alter the mix to use the additional octane. The only improvement is in the mind unless you use blended fuels such a supermarket stuff. If you have an "old" carb engined car then you do get improved performance as there is not an ECU trying to alter the mixture correctly. The stuff is a con.
About a year ago we did a load of tests on the fuel including 3x1000 mile tests in various cars including my HGT and the performance steadily got worse until a return was made to Esso Super Unleaded.
Always run your Bravo/a on a quality fuel i.e. Esso, Shell, Texaco etc. If you can afford to run your 155 HGT on Esso Super Unleaded then go for it
Lastly, if anyone here is old enough to remember the Forumula Shell fiasco will have tried this with as much trepidation as I did - oh and my wife worked for Shell before she gave up working as a bad idea.