tuned for 91 octane and filling with 98ron fuel will that cause problems

[Adrenaline]

Hey guys bought the car from us with a 91 octane tune and in my country we dont have 91 so will it cause problems if im filling with 98Ron

[dansmith180]

Might not run as well as it would on 91 but ECU will adapt and will be fine, if you were tuned for 98 and put in 91 then you might feel a real difference but you should be fine

[GrayMK5GTI]

Will probably run better!! 

In the UK, our cars are mapped to run on basic 95RON. Most of us on the forum run 99RON and notice a huge improvement 

The Bosch ECU will adapt for better fuels (or worse fuels).

[rosco07]

91 US Octane = 95 RON

93 US Octane =98 RON

Is 95 RON available? 98 RON should do no harm as the ECU should adapt.

[Adrenaline]

We do have 95 Ron is it better to fill with 95?

[GrayMK5GTI]

Look in the fuel flap to see what the car is configured for.

Highest octane is best. End of 

[Scottymon]

Use the highest octane for sure.

[Adrenaline]

Thanks guys will do for sure