Sorry to resurrect an old thread.

First full fill on mine was 28.98 MPG by my calculations, 30.8MPG on the computer.

I'm happy to take the mid point as the average, so 30.5 on a mix of driving works for me.

Or, to put it another way, 370 miles for £80 quid instead of £110 in the Disco. Add in the grin factor of what you can beat off the lights, and I'm more than happy with that. 2011 MY SD4 HSE + planning some interesting stuff
Previously: 2004 Discovery Td5 ES Premium + lots of stuff
Previously: P38A Range Rover 4.0 SE
Hampshire and Berkshire 4x4 Response Founder and Treasurer

To resurrect the thread again I have been running my SD4 for the last 800miles on Shell V-Power diesel. I have also been comparing the OBC against the brim/brim figures and have to say I am surprised how inaccurate the OBC is. My journeys have been a combination of A and B roads, motorways, town driving plus short traffic jam trips.

Over the 800 miles, the brim/brim method returned approx 27mpg whereas the OBC is indicating approx 32.5mpg. This is a discrepancy of approx 20% which is poor, if true.

However, I have other discrepancies with the fill-ups. The Freelander tank is 68litres or approx 15gallons. I have noticed that filling up from just under half resulted in 11gallons going in! (and this is not a one off). Just under half a tank should result in only 8-9gallons going in unless the fuel tank is not linear, (i.e upper part of tank holds more fuel).

I only ever fill up from the same pump in the same Shell station so I am beginning to wonder if the pump is under delivering. This would explain why I get more in than I would expect, plus would cause the discrepancy between the OBC and the brim/brim figures.

The next fill up I will be trying a different pump. I am also considering filling up a fuel can (at my normal pump) and comparing the stated delivery volume against what I actually get (using measuring jugs).

It's not likely to be the pump if it's a long term measurement that you've made. The pumps are checked/calibrated by trading standards and are sealed units . my OBC is between 5 & 10% out compared to tank full calculation. There are so many potential errors I the OBC calculation that it can only be a rough guide.

Yes, I agree the OBC is not to be relied upon specifically but there is rough, and there is rough - it needs to be at least reasonably close otherwise it is pointless supplying this facility.

Your 5-10% seems very reasonable but mine significantly more inaccurate. I would have thought the performance of the OBC would be reasonably comparable between cars. This is what made me wonder about the pump.

I don't know what data the OBC is using to calculate the mpg - I assume it's using measured tank volume via a tank float and miles covered (but might be using a flow meter in the fuel line/pump for all I know). It doesn't take much of an inaccuracy in the measurement of fuel in the tank due to a poorly adjusted tank sender for the mpg shown by the OBC to be out - a sticky float, a slight resistance in a wire or joint could produce a reading that's marginally higher or lower than actual. Compound this error with varying tyre sizes and any errors/uncertainties inherent in the calculations and it's not difficult to get 10 or 20% errors.

I'm never quite convinced how full the tank gets anyway - the stupid misfuel device gets in the way and means you can't get the nozzle in properly or see what the level actually is - I fill to the second click-off as that's what we used to do when doing long term car tests in the lab I work in .

Changing to a different pump is not a bad idea anyway - if you do notice any differences then it's worth contacting trading standards - I think the pumps are allowed a very small error but not the sort you are getting!.

The OBC seems to be about 1.5 mpg on the high side throughout the range, I very much doubt it is calculated on tank contents. The amount of fuel that actually gets into the tank is based on the flow rate of the pump and the trigger blowback setting, so second click means nothing unless using the same pump every time and in the same conditions. my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

landy19840 wrote:

Just dont even look! You don't buy a land rover for fuel economy!

Totally agree.

"Fill it 'til it's full .... drive it 'til it's empty".

That's all you need to do, lifes too short to worry about MPG........
..... if you do, get another vehicle [or life]!

 FL2 now gone and have a couple of items left for sale:-

Brodit active iPhone holder + Brodit dash clip,
Bluetooth Music Streaming Module.

I'd generally agree with the sentiment - but a sudden drastic reduction in MPG can be an indicator of something not right with the car - and seeing as it's made by Landrover chances are something somewhere won't be working properly!!

I see nothing wrong with trying to save a bit of money where possible, but you are quite correct that no one buys a Freelander for fuel efficiency. The fuel efficiency was one of the biggest hurdles I had about buying one.

The issue I have, as I mention above, is that I am seeing, what I consider, a too great a discrepancy between the OBC reading and the brim/brim calculations, and I am trying to find out why.

Bubbles, I was under the impression that the OBC uses the ECU fuel map to calculate the fuel being used (so should be in the right ball park) but it is only an estimate, based on a float (or whatever is used to generate the fuel tank level) on what the distance to empty is. The level in the tank would not influence the OBC MPG.

Right, I have filled up again, but from a different pump. My driving this week has been exactly the same mix of motorway, A and B roads, traffic jams etc.
The result is that the brim/brim figure matches the OBC reading within 0.3mpg. This means that the pump I have been using appears under delivering. This is only one fill up from a different pump but I think I am onto something and the pump could well need looking at.
Below are the results from the last four top ups (week between each fill) and interestingly it can be seen to be getting worse.

8.8gal 282mls =32.0
10.0gal 258mls =25.8
10.9gal 260mls =23.8
7.37gal 239.5sml =32.5 – different pump

I will be off to the fuel station to let them know my findings.

This is obviously good news as the OBC seems pretty damn accurate and 32.5mpg for the car is exactly where I was expecting the fuel consumption to be.

Must be a genuine mistake, can't think for one minute that the garage would knowingly under serve their customers, you'll be telling me that their rigging CO2 emission tests next!

Yes, I am not for one minute suggesting it was intentional. As far as I am now concerned, I have found the cause for the discrepancy.

How are you measuring brim to brim, I suggest you could well be 1.5 litres out depending on patience I have managed to fill the tank with over 75litres and I was still not sure it was full. The handbook says usable fuel is 68 litres not the tank size.
I don't know the frequency of tests but Tesco managed to supply fuel at-4% of the measured amount for 9 months. the actual limits are -0.05% and +1% for accuracy my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.

double post error my PC is slightly to the right of Genghis
2012 HSE SD4 In Orkney Grey now gone, best car ever.