Filled the tank up with BP Ultimate instead of the usual cheaper supermarket stuff tonight.
The burble off the engine seems about an octave lower, the car drives smoother and accellerates quicker.
Worth 7p a litre more I'd say.

Engine's getting Terracleaned tommorow afternoon, be interesting to see what that brings to the table.
All good according to folk that have had it done, so should be good.