Since buying my RB5, it has always felt like it has had a misfire @ about 3k revs. More so when warming up in the morning / evening.
Various garages have looked into it and tested "things" and replaced plugs and the MAF, but no matter what people say & do it has always misfired.

I then discovered tesco's 99 ron, and suddenly the misfire was cured.

What's causing this to happen if it's running on optimax etc & has it / will it damaged the engine by running it on anything else than Tesco's 99 ron.
is this a common problem, that can be tuned out of the car?

 

your getting misfire cause of the fuel is ur car an import

 

Thanks for the reply Jockc, but i did say RB5 in the initial messsage.

 

optimax is only 98 maybe u need higher octane try octane boost see if that helps

 

It could be tuned out by means of a remap//aftermarket ecu. It can be mapped for a lower grade of fuel say normal unleaded//super unleaded 97 ron so then you can fill it with whatever you want. The upside of this is more performance as well