I have a 2.2dci diesel X-Trail. The car had 3/4 tank with diesel but put £20 of unleaded by mistake I run the car for 20 miles home it was not running well, I called a company to drain the whole tank, I later filled the tank full with diesel, but now have a warning light emissions permanently on. It runs well for a 1mile or so, but sluggish, but by switching engine off and restarting it runs okay but the emission light stays on permanently.
Get a scan to retrieve the trouble codes and see what it says.
There could still be petrol in system and might take some time foe everything to clear up. Hope the petrol has not resulted in some sensor failure.