"Bad" Fuel? - Ubi
Until this weekend, in the short life of my 325d I have always refuelled with Shell Diesel Extra at one station. I?ve been monitoring the fuel consumption of the car quite carefully and it?s consistently been returning 34.8 mpg actual with 36.7 indicated.

Driving past a different Shell station on Saturday I decided to refuel as there was no queue. I filled it with ostensibly the same Diesel Extra. Since then the engine has been running rough, performance has been down and the OBC indicated fuel consumption has dropped to 31mpg.

Bad batch of fuel?
"Bad" Fuel? - Happy Blue!
Quite possibly and probably water.

I remember filling up at a small station in London several years ago. I was in a BMW 730i and the car ran beautifully normally. I started up the M1 immediately after filling atnd after about 30 miles I thought the car was missing. My passenger didn't notice anything so I ignored it. However after about 60 miles even my passenger could feel the car hesitate even though the cruise control was on about 75mph.

At the next station, I toppped up the car and thereafter ran relatively Ok, although consumption figures indicated an increase of 10% until all the water(?) had gone through the system.
"Bad" Fuel? - Ubi
Water, not being compressible, sounds a tad sub optimal in an engine block. I think I'll brim it from my regular supplier today and hope to reduce the ratio of whatever might have been in the "bad" batch.

Maddeningly, I usually keep my fuel receipts until I've used the related fuel. I carelessly put this one in the shredder.
"Bad" Fuel? - Collos25
I thought diesels had water traps.
"Bad" Fuel? - jc2
Not only do the cars have water traps so do the filling stations;you won't get any water out of a garage with a reasonable turnover of fuel.
"Bad" Fuel? - Happy Blue!
I think that is the point. Small station, low turnover = problems in my experience. High volume station, few problems.

Ask Honest John

Value my car