knotty - you'll most likely notice a much better gain in a turbocharged car by switching to a decent fuel.
I have to say it's never entered my head to put anything other than 95 into my 8v, I just don't think it will show enough benefit to warrant the cost difference.
In my Impreza however (sorry, probably a swear word on here!) I'd never run it on anything other than Optimax / V power. It made a massive difference to both on and off boost running, but then the Subaru EMS is able to "learn" charachteristics of a new fuel as it is always slightly increasing the ignition advance until det is sensed, and than runs the according maps for that det point.
In fact if you had been running on 95 fuel and then switched to 98/99, it was quicker to do an ECU reset as it would learn the new fuel much quicker, otherwise it would take a tankfull to gradually advance and advance over the 95ron settings it was running. The reset would take it pretty much straight to running the 98ron det point.
As far as I know the software in the EMS of the
Ibiza isn't as advanced, I'm certain the smaller cc engines like 1.4 aren't, and therefore any advantages in running the higher octane are going to be slight at best?
