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sean
sean, Technician
Category: Car
Satisfied Customers: 3104
Experience:  UK based Ford Master Technician. Technician since 1984.
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Increased fuel consumption (internet problems)

Customer Question

My 2006 2 litre diesel Ford Mondeo's fuel consumption seems to have increased by 1/3 compared with what it was, and appears to worsen every fill-up. What could cause that? The car seems to be running well. Thanks

Submitted: 2 years ago.
Category: Car
Expert:  sean replied 2 years ago.

Hello, I hope the following is of assistance.

There are many factors that can affect fuel economy. During dark cold days the electrical loads on the engine increase fuel consumption, turning on the air conditioning can increase consumption by around 10%. The type of journeys will affect fuel economy, if you were doing long journeys but now are using the car on short trips around town the fuel economy will reduce. If the change is sudden then make sure there are no obvious causes such as a fuel leak, also check the air filter quality and if unsure of it's history replace the fuel filter. Restrictions in the fuel filter mean that you drive the vehicle in a different way to get the same performance as previous to you noticing the fuel economy change. Check all the rubber turbo hoses for any sign of oil that may indicate a leak, again this would alter your driving habits to get the same performance.

If you use the same fuel station every time then it may be worth changing brands, poor fuel quality has a significant effect on fuel economy, it may take a couple of refills to notice the difference.

If all the above seem OK then it may be worth having a diagnostic check run on the engine management just to make sure there isn't a sensor or actuator concern giving the fuel increase, try a good quality fuel additive to clean any deposits from the injector tips.

Start with these points, let me know if I can assist further or if you have more questions and I'll reply as soon as I'm able to.

Best wishes,

Sean.

Customer: replied 2 years ago.

I reckon the fuel consumption, week by week, has increased by around 16% (ie 1 in 6) over the last few months. I can't remember what percentage of my earlier trips were long distance compared with more recently, but I don't think there's a significant change. I don't use the air conditioning. Lately about 50% of the time has been with the headlights on. I am unaware of any differences in my driving method or vehicle performance.


 


I have been told that if the car is running OK then there should be nothing to worry about. How often can a modern diesel seem to be running perfectly and yet using too much fuel (other than the obvious fuel leaks)?


 


I am very short of money these days and I don't want to end up with expensive tests or part changes (eg injectors) (which will probably cost more than the fuel I'm using).


 


When I bought the car 10 months ago (at 6.1/2 years old) I was amazed how much more economical than my previous Ford 2 litre diesel (at 13 years old) (the salesman prided on its expected economy) it was, but there is no amazement now!


 


I usually use the better grade diesel, and normally use BP (which is recommended) or Shell.. Are there any financial benefits to using *super" grades as the fuel refiners suggest, or is it purely sales talk? (In my youth "super" grades were confined to petrol.)


 


What are these additives? (I go back to the days of Redex in petrol!!) What does one do to ensure of the correct ratio (say add it to a half full tank?).


 


I have so many questions. I know nothing of engine management


systems (petrol or diesel) for example. I have spent a lot of money replacing an alternator in the last few miles (the first dynamo/alternator in around half a million miles) but I guess I'm right in saying that a failing alternator is unlikely to load the engine sufficiently to cause a hike in fuel consumption.


 


I wonder what you have to say about my comments.


 


With thanks, JY.

Expert:  sean replied 2 years ago.

Hello again,

you mention the fuel consumption is over the last few months, this is the start of the dark cold weather, the heated front and rear screens will cause an increase in fuel consumption along with the headlights. With regard to the air conditioning not been turned on, it will turn itself on when the heater is set to demist max to assist in clearing the screen (AC dries air) and will stay on until the driver turns it off.

There shouldn't be an injector concern or anything serious as the car is running OK but the engine management can mask minor concerns, below is a message issued by Ford regarding fuel quality.






20900 - FUEL QUALITY - CUSTOMER COMPLAINING OF
DRIVABILITY CONCERNS


CUSTOMER CONCERNS ABOUT DRIVABILITY, FUEL CONSUMPTION,
COMBUSTION NOISE AND PERFORMANCE FEEL OF PETROL AND DIESEL CARS AND COMMERCIAL
VEHICLES ARE OFTEN RESOLVED BY REPLACING THE FUEL. GOOD QUALITY FUELS, (AS RECOMMENDED IN THE OWNER HANDBOOK) WILL ENSURE THE ENGINE PERFORMS TO ITS OPTIMUM PERFORMANCE. LESSER QUALITY FUELS OFTEN DETRACT
FROM THE OPTIMUM PERFORMANCE WITHOUT SETTING FAULT CODES OR MEASURABLE VALUES
BECAUSE THE ENGINE MANAGEMENT SYSTEM WILL MASK THE EFFECTS BUT PERFORMANCE
DIFFERENCES CAN BE NOTICED.BEST PRACTICE IS TO ADVISE THE CUSTOMER TO RE-FUEL
WITH HIGH QUALITY FUEL. IN SOME CASES IT MAY TAKE TWO OR THREE TANKS OF HIGH QUALITY FUEL BEFORE THE DRIVER
FULLY APPRECIATES THE IMPROVEMENT.
EFFECTIVE DATE: 20/07/2009

There are many companies that sell fuel additives such a Redex or Wynns an example is http://www.ebay.co.uk/itm/WYNNS-DIESEL-INJECTOR-CLEANER-ADDITIVE-325ml-REDUCES-FUEL-CONSUMPTION-/221244654044?pt=UK_Vehicle_Oils_Lubricants_Fluids&hash=item33833581dc each individual additive will have different amounts to add to the tank so if you do use one just follow the manufacturers instructions.

The alternator does put a load on the engine when electrical equipment is used as I mentioned earlier and the greater the load the more fuel is used.

Let me know if I can assist further.

Best wishes,

Sean.

Customer: replied 2 years ago.

I have - these comments were in response to what you said!!!

Expert:  sean replied 2 years ago.

Hello again,

sorry I don't realy understand your reply.

You say "I have". You have what? If you need further information let me know, as far as I can see I've addressed the second set of comments you sent.

Thank you.

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