After I filled my tank with local Co-op diesel on May2 it has been running really rough until warmed up.It misses,stumbles when trying to accelerate and the engine vibrates at idle.The mileage has gone from 31 to 25mpg (all city). It seems to point to fuel but i'm wondering what issue would the fuel have? water? low cetane? winter blend? I usually use Petro Canada diesel and have had no problems up till this last fill.There is no check engine light.