Theroetically - Higher Octane Petrol

[oliver-morrisminor]

I was just wondering,
theoretically what would happen if a higher octane peterol was used in a sidevalve engine?

I recall that when the cars were new octane was about 60.
The lowest octane we can get here in Australia is a 91 or 92. There is also a 95 and a 98 as well.

The car runs fine on this with a lead additive, but I was just wondering the effects of a higher octane level?

[orb596]

I always find that both my MM and sidevalve engined Austin 12/4 run better on Super Unleaded fuel which has a higher octance level than standard unleaded fuel.

[rayofleamington]

The octane rating is a number used to rate the fuel performance.
The baseline for the rating is pure octane (fairly meaningless) - however if you ignore the term itself, the numbers relate to the fuel/air mixture's ability to burn with a progressive flame path at high compression (i.e. higher rating = better).

A low rated fuel will give more 'pinking' unless the ignition is retarded a lot - with retarding, this further reduces the power.
A high rated fuel will run with more advanced ignition which in turn increases the peak power and improved efficiency.

[mike.perry]

Up to a point, after which it would make no difference to the side valve engine, which was designed to run on 80 octane, only to your wallet.
When I was in the TA our Land Rovers were set up to run on 95 octane pump petrol which they did reasonably well until the 1st refuel with pool petrol on excercise in Germany, after which they pinked like mad for two weeks until they were refilled at the petrol station back in this country

[JOWETTJAVELIN]

Complete waste of money on petrol for this engine - use a cheap grade and decoke now and again.