Mixing RON/Octane Fuels

[RevolveR]

I filled up with ASDA 95 RON fuel a couple of days ago and my car is running strangely, especially when the engine is cold. It seems to jerk about a bit (like its about to stall) and then goes fine again. I don't remember it doing this when I was using Tesco Momentum fuel.

I've just been reading about RON/Octane and how pistons can get damaged if you use the wrong type. My car's manual says 98 RON fuel is recommended. If I go and brim it now (the tank is 50% full of ASDA fuel) with Tesco 99 Momentum will it be ok? In my mind I'm thining mixing 99 octane with 95 octane will give me an average of 97 octane or is this silly?

[Output Flange]

No idea what car this is, but if 98RON is "recommended" rather than "compulsory" then the petrol is unlikely to be the cause.

However, topping it up with 98 or 99 is a sensible first step.

[Raize]

It will give you 97 RON.
If your car has an ECU that can detect RON and adjust timing appropriately you'll be alright though. It's only really older cars that you can damage this way.

[mrmr96]

Raize said:

It will give you 97 RON.
If your car has an ECU that can detect RON and adjust timing appropriately you'll be alright though. It's only really older cars that you can damage this way.

You also have to be revving the tits off it for it to make a difference.

[Si_steve]

You'll be fine.

If I can only get 95Ron I'll just put in maybe £10 worth till I can get to a station with higher Ron fuel and then too it up...just makes the car negatively adapt on mine which just means disconnecting battery for 10min to let the ecu reset.