Technical Accuracy of MPG readout

[Pandabloke]

Myrtle is a '57 plate 120 multijet, running normally, no tampering with EGR valve. We've done 32,000 miles+ in 14 months and am getting a total average of just in excess of 42mpg brim to brim.

COMPLETELY IGNORE THE MPG METER. IT IS TOTALLY INACCURATE AND HAS A MIND OF ITS OWN!!

I recently got 37mpg and the meter showed 36mpg and next I got 42mpg and the meter showed 36.9mpg! I have kept as accurate record of my consumption figures and the best has been slightly over 47mpg and the worst about 37mpg. At no time did the meter remotely match the actual mpg.

Oh and my sat nav and multimap mileages have been within a mile or two (literally) of the tripometer. I use them regularly as I am a Chauffeur and I have to record individual distances.

I think the computer cocks up in the conversion or as suggested, uses American mpg. Probably both actually.

Don't forget that idling (ticking over) massively effects the mpg, particularly as recorded by the meter/computer. Just pull up somewhere quiet and flick onto the mpg setting, tick over and watch the mpg slowly drop. It's quite amazing.

Oh (again) tyre pressures are quite an influence to the Multipla MPG I have found. The worst mpg I got was after it came back from having the alloys resprayed under warranty, and the pressures were 1 bar below what they should have been.

 

[BikeDoc]

I don't often look at the MPG readout, partly 'cos it's so depressing with the price of diesel as it is , and partly 'cos no matter what I do, it always seems to read around 34-35MPG ...or so I thought.

After spending just over £60 to fill a nearly empty tank yesterday, when I left for work, I reset the trip and decided to see if I could get the MPG readout to change significantly.
Didn't go above 2000 revs through the gears, stuck to around 60-65mph max on the Motorways (and sat behind the artics when I could ).

Round trip is 41 miles (26 is Motorways).
It took me approx 3mins longer (each way) than usual (usually do 80-ish on Motorways and gearchanges at 3000-3500) and I got 43.5MPG (readout) .

I'll have to do it the old fashioned way as well, keep a record of the fuel bought and mileage done for a few months.

 

[BikeDoc]

Got it to 49.3 last night on the way to work (lots of lorries to slipstream on the motorways), 46.5 on the way home (empty roads).
I'm determined to get it over 50 now , I can see this becoming an obsession

 

[BikeDoc]

Ha!
Got it up to 58mpg today
I can keep it to a minimum of 45 around town now as well.

60mpg here I come...

 

[Peat]

I bet you few people have managed 99.99 mpg.

I was able to get that reading by using a trailing throttle on a down hill gradient of approximately 2.6 miles.

I loved it. Unfortunately I no longer go that way but I do get approximately 44.5mpg on a regular basis just running around town with the odd A14 mileage.

Be happy

Peat

 

[BikeDoc]

Coast, you'll get even more (though I guess it can't show anything above 99.99).

 

[MultiPa]

... drove all the way to Brittany, did some sight seeing and drove home and did 1500.9 miles ... cruising at around 80 mph with 3 adults, 2 kids and a boot rammed with luggage and a/c on the on board computor read 33 mpg ... on the way back i did 90mph most of the way and got it to 30mpg on the computor, and used exactly 3 full tanks running each dry [when it no longer predicts a range] so around 60 litres / fill.

180 litres / 1500.9 miles is 37.9 mpg. Not too bad considering speed and load?

 

[chr1s]

We've done 32,000 miles+ in 14 months and am getting a total average of just in excess of 42mpg brim to brim.

COMPLETELY IGNORE THE MPG METER. IT IS TOTALLY INACCURATE AND HAS A MIND OF ITS OWN!!

I recently got 37mpg and the meter showed 36mpg and next I got 42mpg and the meter showed 36.9mpg! I have kept as accurate record of my consumption figures and the best has been slightly over 47mpg and the worst about 37mpg. At no time did the meter remotely match the actual mpg.

With 56 full to brim refuellings and 31,000 miles, in 2½ years, I have also averaged 42 mpg.

But over that time, the average fuel consumption (brim-to-brim) divided by the average displayed fuel consumption (trip computer) works out as 1·25, which is exactly the relationship between Imperial and US gallons.

As shown below, the brim-to-brim calculations vary from 14% to 34% above the trip computer display, so it works as a rough guide to fuel consumption, as long as you remember to add 25% to it.



Interestingly, after fill-up 26 I changed jobs with a longer journey to/from work. The increased fuel consumption with a warmer engine and fewer stops is noticeable.

 

[martinash]

we have a 2004 with around 60,000 on the clock, we find that average driving thats and mixture of local and very little motorway we average around 42mpg on a long run with a roof box and taking it easy it drops to around 32mpg without the roof box around 38mpg so we find it better around town than on the open road.

Mash

 

[MultiPa]

But over that time, the average fuel consumption (brim-to-brim) divided by the average displayed fuel consumption (trip computer) works out as 1·25, which is exactly the relationship between Imperial and US gallons.

As shown below, the brim-to-brim calculations vary from 14% to 34% above the trip computer display, so it works as a rough guide to fuel consumption, as long as you remember to add 25% to it.


Interestingly, after fill-up 26 I changed jobs with a longer journey to/from work. The increased fuel consumption with a warmer engine and fewer stops is noticeable.

Looks like a decrease in consumption to me

Very pleased with this information over such a long period - adding 25% to my trip gives 54.7mpg for my first 1,000 miles (2001 JTD with 99,000 miles).

Get me with the light foot!

 

[taxiadam]

After filling up and driving as best i could to the speed limits as I went to and from work I've managed 664 miles on 68.88 litres of diesel. I think that works out to 43mpg.
This is my best ever on one tankfull. As you know the Multi has a 70 litre tank and I put 68.88 in thats very close to empty!

I just sold my 1.9 x reg diesel and I usually got around 38mpg diving like a dickhead.

 

[MultiPa]

I just got my best ever figures over a decent distance - in this case it was Rotherham to South Manchester - about 60 miles over Woodhead Pass and the Pennines on a wet and windy day.

Still not done a brim to brim check to see if my computer is pessimistic, but if it is 20% out as most seem to be then I've driven a 6 seater bus over the Pennines on a windy day, in about the same time as google maps said it should take, and got somewhere north of 60mpg. Otherwise I've still done over 50mpg, which is good enough for me!

(airbag turned off because of baby in the front btw)

 

[rc3675]

I've had my 2004 1.9Jtd Dynamic Plus for a month now.
It's done 1117 miles, started with a full tank and subsequently done 2 brim to brim fills (total 105.09 litres). This gives an actual mpg of 48.3. The computer shows 36.7 (which is 30% out).

The 36mpg is scary, however I'm very happy with the 48mpg as I was only expecting approx 45 from such a big car

The first tank ful was with Tescos standard stuff (the nearest station to the dealers) and the 2nd tank was Shell fuel save, but also had a bottle of comma diesel magic in it (which could have affected the consumption). I'll keep a track over the next few tanks and see if it stays consistent.

 

[Pandabloke]

..... As you know the Multi has a 70 litre tank .............QUOTE]

Actually, I think the facelifts have a smaller tank. I cannot get more than 59 litres in my '57 plate no matter how hard I try or how low I run it (suicidely low, sometimes)? Used to get near 70 litres in the uglybug.

 

[pete123]

Do you regularly reset the trip to clear the old mpg data?

I get about 40-42 for commutting, 30 mile round trip with some dual carriageway and some town driving.

how do u reset the mpg to as mine reads 38.4 over 11000 miles and have tryed pushing every button 2 reset this thanks

 

[rc3675]

how do u reset the mpg to as mine reads 38.4 over 11000 miles and have tryed pushing every button 2 reset this thanks

1) You must be stationary.
2) Press the trip button till either Trip A (or Trip B if available) is shown
3) Then press and hold the Trip button.

The key is being stationary.

 

[pete123]

Hi again I'm reading 42 to the gallon with a heavy foot what am I actually getting is it this reading as read about this 20 per cent but people tell me its 20 percent under what it reads or is it 20 above

 

[megan1413]

i was only getting 46mpg but when reset both trips i now average 60mpg on dual carriageway

 

[Rikstaparr]

How do you reset the trip?

 

[pete123]

How do you reset the trip?

3 threads up will help u