sunbeamtiger.co.uk

On returning from France recently I filled up with 95 octane petrol at an international brand garage in Folkstone and right away engine performance fell away. Misfiring through the rev range above 2000 and generally spluttering all the way home. I'd run out of the the additive / octane boost I use as a rule and wonder whether that's my problem or is there something wrong with British petrol nowadays!
I avoid supermarkets for the Tiger but thought the main Esso, BP etc brands were safe.

What's others experience? Have you encountered poor 95 octane unleaded and had any problems?

I haven't refuelled yet but I will be trying 98 RON when I do, even though this will hit the wallet!

STOCTiger

Your engine may be set up to run on high octane fuel, ie it might have high compression, and/or ignition is well advanced. But using low octane usually causes pinking, rather than misfiring.

You may have got some contamination in the fuel. There was a case in point recently with poor supermarket fuel. But its very unusual.

Thanks for that Chris.
Having changed the carb, coil, condenser, points etc, etc and having drained the tanks and fueled up with 97 RON petrol the motor now runs well. The considered opinion of the two pals who ran through the diagnostics was that the root problem was timing not nasty petrol.
Just need to get in a decent road test to be sure!

Thanks again for giving your views. Seems a shame that so few are willing to do the same!

"STOC Tiger"

yes, misfiring shouldn't happen with low octane fuel. the only effect should be pre-combustion (pinking). its likely you got some dirt in the tank from the petrol you put in if it only started happening then.