Thread: Shocked at fuel consumption

Clearly something is wrong - as the OP just used the display fuel consumption my guess it that is it something to do with the display.

If it were mine before doing anything expensive I would go to the garage and fill with petrol.

Before leaving the garage, park in an out of the way section and reset the displays. Then to a hard reset of the computer systems. After all that is done start driving around and I bet the fuel consumption display starts displaying a reasonable figure - after about 200km refill and check actual usage and I bet it is Ok - about 10% more than the display.

If actual fuel consumption is still up around 35l/100 and not around 15l/100 then it is time to do the more expensive diagnostics.

Garry

Maybe also feel how hot your wheels are after a trip - if the brakes are binding, they will be extra hot!

Ignore the trip computer. It'll be calculating on old data. If you do the math you should be seeing 15-20 depending on how hard you drive it.

Don't think so, the OP said he's done 136km after brimming the tank with premium and already used more than half.


If the guage is anything like the TDV6, halfway on the gauge means you've used more like 60% of your fuel, so he could've used up to 70% of his fuel based on that logic, but let's assume he's only used 50%.
The tank is 90L.
Let's assume he's used 45L to do 136k.
That equates to 30.2l/100km.
As a bloke that does 750km per week this is daunting!


I'm not sure how the fuel usage is calc'd on our LRs but I do know on VW/Audi vehicles it's measured off of fuel returning to the tank compared to fuel taken every 40m of distance travelled. It's quite accurate, and if LR is like this, it's impossible that the fuel gauge and fuel consumption readout would both be wrong, as they are effectively two separate systems.




On a petrol, first thing I would be checking is:
a) MAF sensor
b) Oxygen sensor
c) does the engine run rough at all?


It'd be perfect if you could use a scan tool to test your MAF output (a rule of thumb for this - do a full throttle run in say second or third gear - your maf reading in grams per second should be approximately 0.8 x your car's peak horsepower).
With a scan tool you can also test the lambda readout of your oxygen sensors. This is the deviation from the stoichiometric air/fuel mix (14.7:1) at any given time. A figure higher than 1.0000 usually indicates a lean condition and less than 1.0000 is a rich condition. It should be a little bit richer on acceleration. The computer uses the MAF and oxygen sensors together to work out whether the burn is consistently richer or leaner than it should be, and comes up with a percentage figure called a long term fuel trim that it uses to adjust mixtures. Not sure about LRs but at least VW/Audi have a trim for idle and one for other conditions.


It is my experience at least, notwithstanding a massive fuel leak, (and I trust you'd work it out if you had one!) you'll get a good lead on your problem by checking these figures. Alternatively you can unplug your MAF for a bit, forcing your car to run in open loop mode and run off the oxygen sensor alone. If your economy picks up dramatically, you'll know your maf is at least dirty, if not faulty.

Originally Posted by superquag

Ignore the computer... fill it up again and calculate the Old Fashioned Way. Try doing either 100 or 200 km exactly, - no maths needed.
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What is written above is good advice, all the rest is speculation about something that might not be a problem once your done more than a hundred kilometres or so. At the very least reset the trip computer and once you have used at least a couple of tanks full of fuel then you will have a much better idea.

Plus one other thing, D3 fuel gauges once they get old often aren't that reliable, again that's why filling it up and then doing a 100 kilometres then refilling it will give you a correct fuel consumption, then you will know if you have a problem or not.

Also have a look at some less obvious, potentially just a serious contributors, such as tyres and brakes

Just to rub salt into the wound... Tonight I filled up the work truck, '95 petrol Patrol which tows around 2.5 ~ 3 tonnes.

Just a smidgeon under 26 litres per 100km, for twice the weight plus lots more wind resistance then your toy... (Patrol, plus plant, on a trailer with ramp and big storage bins)

Take it back, it's not 'fit for purpose' or in 'merchantable condition' with that obscene thirst.

And keep us posted !

Edit: In addition to the previous post, (flat tyres/dragging brakes..) . wheel alignment? - you'd know.... there'll be humungous wear on them.

If you are still around, take it back to where you bought it from once you have comfirmed it is faulty.

According to the specs, the fuel tank is 86ltrs and fuel economy is supposed to be 15.2/100k (combined)

Baz.