C5 2.2HDi poor economy

cachaciero · Unread post by **cachaciero** » 27 Jul 2010, 18:40

O.K given that I am now digging into 4HP20 performance on 2.2's and have more questions than answers did the OP ever get a resolution to this?

jimleshed · Unread post by **jimleshed** » 28 Jul 2010, 12:30

My 2.2HDI Exclusive SE has been low MPG since I bought it and nothing I tried seemed to change it.
Most of the time I am just back and forward to work in it, about 5 miles fast roads with 2 miles town traffic. Average when bought was about 31- 32MPG. This is real calculated MPG, not relying on computer which can be wrong.

Eolys filled and working - no change
New DPF in exhaust - no change but top end speed improved.
New Air filter - no change
Italian tune up (when I ripped off the undertray on the M5) - now up to 34.1MPG - ok, this may be down to having all the undertray now fitted properly and not waving about as I drive.
Next step is to try some injector cleaner and see if that does anything. But i am pleased that eventually it seems to have got a bit better!

Note - Italian tune up = blast down Mway at top speed.
Legal advisory note, dont break the speed limit....

Unread post by **Old-Guy** » 28 Jul 2010, 12:46

I wonder if Jim Le Shed has put his finger on the cause of your problem - it led a sheltered life when new so the engine has never bedded in and 7 years of gentle motoring (and cheap supermarket diesel) has coked up the engine.

If it uses some oil when driven hard, that would tend to confirm.

Fill it with Shell or BP premium diesel and give it some welly.