Hi All,

Over the last 2 weeks i have noticed a sudden drop in MPG in my 2012 Cmax 1.6 TDCI Titanium. I used to receive on average between 44-48 MPG around town / driving to and from work (10 miles trip).

However I have recently noticed that on the same journey, and same usage getting around 40-41 mpg - engine sounds fine and doesn't appear any loss in power.

Does anyone have any suggestions on what to check as something isnt quite right!

Thanks

Diesel engines take longer to reach optimum operating temperature in colder weather & are as a result less economical.

How are you measuring the vehicle's average m.p.g. ?

I use the trip computer for ease, however I know this isnt true MPG and i actually get 2-3 mpg less than this.

I have noticed the fuel guage go down further based on miles done so I assume its not a sensor issue? Would it be worth getting a diagnostic done? Would it bring up anything that the car wouldnt tell me?

Thanks for your help!

When was the fuel filter last changed ?

It had a service about 4k miles ago so I would assume then.. however I will need to check to what exactly was done - could a blocked / clogged fuel filter provide a sudden drop in mpg?

The colder weather naturally reduces MPG anyway. The colder air is more dense, which needs more fuel adding to the ratio to give the right bang.

Yes, a poorly functioning fuel filter will cause a loss of m.p.g.

It had a service about 4k miles ago so I would assume then.. however I will need to check to what exactly was done - could a blocked / clogged fuel filter provide a sudden drop in mpg?

Never assume anything.

When was the fuel filter last changed ?

Havent we been here already today? Lol

The colder weather naturally reduces MPG anyway. The colder air is more dense, which needs more fuel adding to the ratio to give the right bang.

Yes i understand this, however it hasn't really got cold yet and during the 2 winters I have owned the car for it hasn't noticably affected performance!

Never assume anything.

Sounds like a voice of experience...! I will check the log and come back to you later.

Today & yesterday & so on & so forth . .

A million times Ian . . . we can almost predict the answers to the questions we are asking . . . :)

I must admit, fuel filter is the best shout at the moment. I had mine changed a few days ago, it makes one heck of a difference. I would also suggest for best performance, replace the air filter too.

The M.A.F. sensor is another potential culprit & is always worth a look & clean up if required

MAF sensor. What is it and where is it located please?

MAF Sensor - Mass Air Flow sensor, its in the housing to the air filter, where you see an electrical connector.