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longtomsilver

Car Just Been Serviced, Fuel Economy Diabolical. Why?

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As the title suggests just had our 2.0l VW diesel serviced (60k) we our now getting only 53mpg, last week we easily achieved 60mpg+

What's changed, what have they done wrong (they have replaced the air filter).

Edit to add: also now getting 35mpg in town as opposed to 45mpg previously.

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As the title suggests just had our 2.0l VW diesel serviced (60k) we our now getting only 53mpg, last week we easily achieved 60mpg+

What's changed, what have they done wrong (they have replaced the air filter).

Have they put a massive spoiler on the back?

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Does your car have a computer that tells you the mpg? Could be they disconnected the battery and the computer reset and has to re-learn before it gives accurate estimates.

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When I take mine for its annual service and MOT at Nationwide Autocentres (I get it free with Tesco loyalty points, otherwise I'd do the service myself), they always want to put some fuel cleaning additive in the tank at a cost of £20. They give me the sales talk about how it'll reduce the chances of the car failing the emissions test, will help all sorts of things run better, etc. etc. The first time they tried to flog me this crap I gave in and let them do it. The only discernible result was that for the remainder of that tank of petrol, fuel consumption dropped from 48-50mpg to 40-42. After the next fill-up it recovered to 45-46ish, and by the fill-up after that was more or less back to normal. I later looked the additive up on the net and found some pretty credible sources (e.g. Honest John) claiming that there was no evidence that it had any significant effect, and so I've resisted the sales talk in subsequent years.

The only other possibility I can think of is that they put the wrong sort of oil in.

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1. If you've not had it changed yet, change the cambelt, tensioner and water pump. NOW.

2. Was it a major service ? Did the battery come off or did they do a reset. Most modern diesels adapt their performance to your driving style over a period. If it's been reset, then it'll take time to come back up.

3. If they touched the brakes, see if you get more brake dust on the wheels than before - if so, that.

4. Did they put new tyres on ? What kind - the same as the last ones.

5. What are your tyre pressures now - were they overinflated before. Makes a big difference.

6. Turbo diesels (please God tell me it's not a Golf SDI....) perform worse when it's warmer.

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My mileage was 37 mpg before a service and when back it was 32mpg! I reset it and it got back to 37mpg eventually.

Did the car have a fancy ECU that tailored the car's tuning to your driving? Might take a while to settle down.

As mentioned , too thick oil, binding brakes (including hand brake) air leaks in hoses (worth checking all hoses under the hood).

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Fixed the computer that gives the readings :lol:

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As the title suggests just had our 2.0l VW diesel serviced (60k) we our now getting only 53mpg, last week we easily achieved 60mpg+

What's changed, what have they done wrong (they have replaced the air filter).

Edit to add: also now getting 35mpg in town as opposed to 45mpg previously.

Your driving skills have begun and downward trend?

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I'm only getting 37 mpg from my Almera diesel but I'll chalk that down to mainly urban use. :rolleyes:

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As the title suggests just had our 2.0l VW diesel serviced (60k) we our now getting only 53mpg, last week we easily achieved 60mpg+

What's changed, what have they done wrong (they have replaced the air filter).

Edit to add: also now getting 35mpg in town as opposed to 45mpg previously.

Check they have put the correct air filter in and the right way round, a common mistake, and that the air filter cover is on correctly. These will both effect your mpg.

You can check if your breaks are binding by driving up the motorway for a bit not touching the brakes and then COASTING to a stop in the services, get out and throw some water from a bottle on your brakes, if it sizzles binding breaks, nb don't touch them to see if they're hot because that's a really silly thing to do.

My bet, air filter wrong size, wrong way round or cover not on properly.

HTH

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Check they have put the correct air filter in and the right way round, a common mistake, and that the air filter cover is on correctly. These will both effect your mpg.

You can check if your breaks are binding by driving up the motorway for a bit not touching the brakes and then COASTING to a stop in the services, get out and throw some water from a bottle on your brakes, if it sizzles binding breaks, nb don't touch them to see if they're hot because that's a really silly thing to do.

My bet, air filter wrong size, wrong way round or cover not on properly.

HTH

Thanks everyone for their input and wittys - shame there isn't a like function on here, made me smile.

I was thinking it might be something to do with the airfilter?? other suggestions gold(I wish) and spoiler a little far fetched :D. It is a company car and it was serviced via arval so I assume they've done the cambelt. If the fuel economy doesn't improve by the 2nd tank then I'll be on to the garage - it's annoying that the trip computer is hinting at a 525mile range as opposed to the cars career average of 650+ I too thought a service led to an increase in MPG :(

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Check they have put the correct air filter in and the right way round, a common mistake, and that the air filter cover is on correctly. These will both effect your mpg.

You can check if your breaks are binding by driving up the motorway for a bit not touching the brakes and then COASTING to a stop in the services, get out and throw some water from a bottle on your brakes, if it sizzles binding breaks, nb don't touch them to see if they're hot because that's a really silly thing to do.

My bet, air filter wrong size, wrong way round or cover not on properly.

HTH

Yep, air filter and housing would be my first area of investigation too.

Would also add checking the connection wire to the air flow meter which could well have been removed to make the filter change easier and then not replaced or it's just come loose from the assembly being pulled about.

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When I take mine for its annual service and MOT at Nationwide Autocentres (I get it free with Tesco loyalty points, otherwise I'd do the service myself), they always want to put some fuel cleaning additive in the tank at a cost of £20. They give me the sales talk about how it'll reduce the chances of the car failing the emissions test, will help all sorts of things run better, etc. etc. The first time they tried to flog me this crap I gave in and let them do it. The only discernible result was that for the remainder of that tank of petrol, fuel consumption dropped from 48-50mpg to 40-42. After the next fill-up it recovered to 45-46ish, and by the fill-up after that was more or less back to normal. I later looked the additive up on the net and found some pretty credible sources (e.g. Honest John) claiming that there was no evidence that it had any significant effect, and so I've resisted the sales talk in subsequent years.

The only other possibility I can think of is that they put the wrong sort of oil in.

They put the additive in because it costs them 2 quid.Nice mark up.

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Chances are that you are looking at an average consumption figure. Your car has been sitting idling for some considerable time during the service and this period of 0 mpg has brought the average down.

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  • 309 Brexit, House prices and Summer 2020

    1. 1. Including the effects Brexit, where do you think average UK house prices will be relative to now in June 2020?


      • down 5% +
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      • Even
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      • up 5%



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