Help with Vito Traveliner 2004: Fuel Consumption gone up after service

I took my Vito (2004 model) to MB dealership for 34000 mile service.
Immediately after that the diesel consumption went up. I now get 28 miles per gallon.
Before the service I used to get 34 mpg. I took it back to the dealer and although they confirmed that fuel consumption was up, they don't know what has caused this.
Right now, they have no solution to the problem.
Is there anything that I can do.....or do I have to live with it.
Any advice would be welcome.
Thanks in advance....
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I'd check for fuel leaks. It's probably way different nowadays, but the return lines that port unused fuel back to the tank in earlier diesels used to get cracked and leak... Can you smell diesel fuel near the engine?
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Thanks for the tip.
No smell of any fuel leak but I will ask the question at next service.
Regards
<William P.N. Smith> wrote in message wrote:

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What exactly did they do to your vehicle?
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Hi Martin
According to the invoice, they have changed the Engine Oil, Oil Filter, Pollen Filter and Fuel Filter.
The car runs smoothly as before and there dosen't seem to be any other changes.
Hope you can help....
Thanks in advance.
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Did they possibly change the type of oil, for instance from a 5w-30 syn to a 20w-50 dino? This could cause a loss of mpg. Paul
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Hi Paul
I have no idea about the oil, but I will ask them and see what happens.
Thanks for the tip. I will let you know what happens.
Thanks again.
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