It all depends upon your engine whether Super Unleaded is worth the extra money.
If the engine is designed for 95 octane unleaded (also referred to as EuroSuper on the continent) it makes little , or no , sense to feed it a diet of higher octane, from a engineering viewpoint.
The one exception to this is if the ecu is capable of making use of the additional octane by advancing the ignition timing. Many of the modern units used by Morgans with their sophisticated management systems can make use of the additional octane. I am afraid I don't have enough knowledge to specify which particular engines, except with the +8.
The early Moss Box cars need Super Octane to cope with the 10.5:1 compression ratio. When the compression ratio dropped to 9.25:1 it could be fed a diet of 95 octane , but on early cars this could be a bit marginal , so occasional tanks of Super are probably a good idea. When the injection systems came in first "Flapper " and then "Hotwire" or "GEMS" none had any knock sensors, so 95 octane is enough. However the GEMS system does have the ability to detect knocking , but MMC did not fit the knock sensors ;-) Some owners did retrofit these and these cars can benefit from a diet of the Super Unleaded for the extra performance.
The old tests of listening for knocking when wide open throttle is used as the engine is under high loadings from low speed will only detect one type of pre-ignition. This can generally be "driven around" by using lower gears and not letting the engine slog. Far more damaging to the engine is high speed pre-ignition which is encountered mainly on German autobahn type driving (continuous high speed) You cannot detect this by ear.
Last edited by MOG 615; 30/04/15 10:44 AM.
