2009 E350 MPG....Mercedes fraud

[liamski007]

well maybe that headline grabber is a bit unfair as we all know that manufacturers' MPG statistics and 'real-world' statistics are two different things. However, I have been doing my own MPG experiment for a few months now and I'm quite appalled to report that the Merc quoted stats for my car are out by about 14%...I'm getting around 37mpg against the 42mpg reported by the car's on-board computer. As I say I've repeated this experiment numerous times and the sums are correct. I drive around 20k per annum and my run to work (around 25 miles each way) is through some towns and country roads so I'm reasonably happy with 37mpg give that the car is a 3litre V6 but when are manufacturers going to start being honest with us. For the record I calculate my MPG as follows:

1. fill the tank right to the top (after foaming of diesel) so that I can see the diesel at the lip of the filler
2. set the trip meter to zero
3. re-fill after a week or so to the exact same place - lip of the filler
4. note the litres taken to re-fill and miles undertaken
5. divide the litres by 4.54 to get gallons and divide this into the miles done

When I hear people (on here) talk about MPG figures, I often wonder are they simply quoting what they see on the computer or have they actually worked it out.

 

[MancMike]

You're calculating using 4.546L per gallon, which is UK gallons. I think these mpg figures are quoted using US gallons, so you want to use 3.785?

Check out fuelly.com it lists real world tank to tank MPGs for cars including their variants.

Also I think there's an area of honestjohn that lists something similar. It shows real world mpgs of different cars and shows it's percentage of the manufacturer quoted figure. Some are very low, like 57% or less. I think my engine does particularly well at about 97% which mirrors my experience too.

 

[whitenemesis]

Both my C class and my CLS trip meters agreed with my brim-to-brim calculations to within 1%. Perhaps yours needs investigating, not sure if it can be adjusted using STAR?

 

[fuzzer]

The computer in the car will be calculated for a uk gallon.

 

[liamski007]

no....what? that can't be right!! A UK car giving me my MPG based on US gallons...that would mean my real world MPG would be significantly worse.

 

[liamski007]

well that's impressive Whitenemesis - I wonder can the software be re-calibrated??

 

[Red C220]

The OBC on our E class consistently over reads by about 10% (we get at least 10% worse mpg than the OBC claculates).

The OBC on our SL is almost always within 1 mpg. It's very accurate indeed.

 

[liamski007]

well I checked out fuelly.com (only one user with same car as mine) and she was getting 36mpg...which is more or less what I am getting. I also checked out honestjohn and the result is 36mpg real world against 47.1mpg official Merc statistic...which is even more appalling. I mean there there really is no point in manufacturers having this information in the on-board computer if it is so mis-leading.

 

[liamski007]

RedC220.........good that you are getting such accurate info in your SL...I wonder why Mercedes can't they use the same reliable technology between their different cars

 

[whitenemesis]

RedC220.........good that you are getting such accurate info in your SL...I wonder why Mercedes can't they use the same reliable technology between their different cars

They can and they do, there's obviously something else affecting the accuracy, some setting/calibration perhaps

 

[MancMike]

All the figures are there;

On average cars achieve 84% of their quoted figures.

Mercedes-Benz achieve on average 83% of their quoted figures.

So it's not a scandal is it? 83% is higher than a lot of the mass car manufacturers listed.

Mercedes-Benz C-Class (2007 - 2014) - Real MPG | Honest John

Mine is a 280 which is the highest in the list at 99%

 

[MancMike]

Are you sitting with the engine running for any periods of time? That's obviously zero miles per gallon and will pull your average down.

 

[liamski007]

To be honest, I would rather not have MPG information at all on my OBC than be given inaccurate information....I mean, why bother. I've stopped using it and in fact it annoys me when I scroll past it and I see the fraudulant figures on display.

 

[liamski007]

very occasionally sitting idle, but I'm not talking about bringing my MPG figure down...that's not the issue. The issue is that the OBC figure is so different to the real world figure. If I'm sitting idle the OBC computer should still be able to record my fuel usage and my miles covered and do the maths.

 

[Deleted member 6183]

Golden

 

[Dryce]

well maybe that headline grabber is a bit unfair as we all know that manufacturers' MPG statistics and 'real-world' statistics are two different things. However, I have been doing my own MPG experiment for a few months now and I'm quite appalled to report that the Merc quoted stats for my car are out by about 14%...

People go about quoting their dash computer mpg readouts - so manufacturers play games and it keeps the customers quoting and discussing these numbers happy.

I always reckoned on 10% to 15% optimism in the past so what you're seeing is in the normal ballpark for these things.

 

[wil992]

I reset the counter on my car when I got it and haven't touched it since.
The car reports that I have averaged 23.3 mpg over the 5794 miles I've done since I got it.
I also have a phone app that I use to input all my fuel and mileage, and that works out that I have actually achieved 23.18 mpg.
Overall I'd say that's pretty accurate, so if yours is so far out it looks like something is amiss either with the car or your calculations.

 

[wil992]

Also, your initial post is a little confusing to say the least. You keep referring to the merc quoted figures and not being the same as real world driving etc, but in fact your complaint is about the accuracy of the readout on your car compared to a true calculated mpg figure, so it has nothing to do with the brochure figures for the car at all as far as I can see?

 

[DSM10000]

To be honest, I would rather not have MPG information at all on my OBC than be given inaccurate information....I mean, why bother. I've stopped using it and in fact it annoys me when I scroll past it and I see the fraudulant figures on display.

The OBC reading is an indication, no manufacturer claims it to be accurate, also the MB system seems slow to update, if I leave mine alone then after 5 miles of driving from cold I see 25mpg, if I re-set it at that point it quickly rises to around 30mpg.
As for your "experiment", it is was not carried out under the controlled conditions that are used in calculating approved MPG figures (indoors on a rolling road usually)so cannot be used as a direct comparator. If your figures are consistent over your journeys then all seems fine.

 

[Deleted member 6183]

I bet a few of us have owned BMWs with the 'swingometer' fuel efficiency gauge, I'm not sure that mine was entirely accurate, fraudsters!