help

[bobking]

hi, I'm bob, i bought an 05 X trail a couple of months ago, nobody told me to only use premium fuel and i put unleaded in it. the seller got in touch with a Nissan mechanic and i only use top fuel now. but i have noticed, when I'm at the lights, in drive, foot on brake, the motor seems to be running rough, what, in the old days we would call 'shunting' have i done some damage by running unleaded, or is this a common trait of this model. I'm at a loss, do i need to see a mechanic or not? any help would be greatly appreciated. regards bob