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Fuel/Mileage Computer inaccuracies

This is a discussion on Fuel/Mileage Computer inaccuracies within the CLA General Discussion forums, part of the Mercedes-Benz CLA Forum category; Originally Posted by Capt Torch The 10% difference measured can be the cause of temperature difference of the fuel and outside temperature, The fuel measurement ...

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Thread: Fuel/Mileage Computer inaccuracies

  1. #11
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    Quote Originally Posted by Capt Torch View Post
    The 10% difference measured can be the cause of temperature difference of the fuel and outside temperature, The fuel measurement is not taking this into account, small but still there is always inaccuracy.
    You will need a complete different fuel consumption meter to be accurate. To expensive for cars.
    Hmmm ... fuel temperature relates to achievable power and the fuel rate sensor is just raw material per unit time.
    Though the car knows how many miles have gone by and how much the fuel tank level has changed ... they may want to go back to such basics instead?

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    Quote Originally Posted by Capt Torch View Post
    The 10% difference measured can be the cause of temperature difference of the fuel and outside temperature, The fuel measurement is not taking this into account, small but still there is always inaccuracy.
    You will need a complete different fuel consumption meter to be accurate. To expensive for cars.
    Sorry, can't possibly buy this line of reasoning. 1) Cars I've owned from other manufacturers don't have this issue. 2) The fuel injection system is very precise these days and 10% error is not believable. 3) Consistently over stated by around the 10% mark is not something the MB engineers/QA could accidentally missed i.e. Deliberately making the car look more efficient than it is.
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    Quote Originally Posted by jmc View Post
    @weiyun
    Yes our gauges are optimistic from 1~3mpg which is the ~0.5L/100km differential you are seeing.
    Though even at 6.8L/100km thats 34.5mpg which is pretty darn good considering how much fun the car is!
    I am not complaining about the actual fuel efficiency but the data MB presents to the driver. The systematic error in MB's favour seemed to be no accident.
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    Quote Originally Posted by Northern Al View Post
    When it comes right down to it, if my gauge says I'm getting 42.7 mpg but, I know it's actually 39 mpg . . . it's really no big deal. IMHO, with a car like ours (4-cylinder turbo, aesthetic appearance, handling, features and comfort) getting the same or better gas mileage as a Prius - I'm thrilled. This seems to be just a tempest in a teapot.

    Should MB fix the discrepancy? Yes - but, it's not at the top of my wish list for the model.

    Top of the list: I'd rather them spend their energy in finding a place to hide (and provide) a spare tire so I can give up these damn run-flats!
    I agree about it is what it is. However, the recent VW diesel gate controversy begs the question, are the consistently higher figures manipulated to help match the EPA estimates, that many people use as a factor in helping to choose a car. This probably isn't a huge issue with a lot of members here, but since the EPA estimates have been lowered for the new models, are we looking at a cover up, of sorts?
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    Well, I don't think it's that serious here as the data presented by the dash computer is only for the driver. It's kind of a feel good factor to those who are environmentally conscious. However and as you said, the systematic error is significant enough for some drivers in their choice of vehicle and engine.


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    Two points. first, if the gauge is usually wrong, why is it always a high estimate?

    Secondly, we expect more from MB, the best or nothing at all.
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    Quote Originally Posted by 07SGT View Post
    Two points. first, if the gauge is usually wrong, why is it always a high estimate?

    Secondly, we expect more from MB, the best or nothing at all.
    Same sentiment.

    Obviously I'm only seeing it on one car. Wondering if anyone else have similarly compared with care to verify this discrepancy?


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    Quote Originally Posted by weiyun View Post
    I am not complaining about the actual fuel efficiency but the data MB presents to the driver. The systematic error in MB's favour seemed to be no accident.
    Yes I know and I agree ... anywhere from 3% to 10% over statement of mileage.

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    Quote Originally Posted by Texas Dave View Post
    I agree about it is what it is. However, the recent VW diesel gate controversy begs the question, are the consistently higher figures manipulated to help match the EPA estimates, that many people use as a factor in helping to choose a car. This probably isn't a huge issue with a lot of members here, but since the EPA estimates have been lowered for the new models, are we looking at a cover up, of sorts?
    Not a cover up per se ... but some pal in some agency said dude fix your claims before you get screwed and let the new car year slide ...
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    Quote Originally Posted by weiyun View Post
    Same sentiment.

    Obviously I'm only seeing it on one car. Wondering if anyone else have similarly compared with care to verify this discrepancy?


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    Well I already posted my spreadsheets support your higher than actual mileage reporting ...
    However! As mentioned thats just a gauge ... real world miles driven per full tank is more objective and 38mpg or 6.2L/100km is lofty but possible on a flat stretch at constant nominal speed (eg 65mph) which is a balance between air drag and inherent momentum.
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