Technical Accuracy of MPG readout

[missionary]

2 tanks since I bought mine. Last tank brim to brim was 49.3 mpg over 50 plus litres of use. Its a 2002 110 elx @ 84000 miles.

But I am going for 52 if I can ! So injector clean and calibrate is next on the maintenance list.

cheers
mish

 

[TinyUK]

Ive been reading this thread with interest, my 2002 110 (new to me on sunday) is giving horrendous readings of between 27 round town to 36 on a short run (60 on an A road but only about 5 miles).
My driving style will probably not get me any endurance records as far as MPG goes, but wont get me any points either! Mostly urban mileage and a fairly "average joe" driving style.
Ive only done 30miles or so in it so far and i realise I havent really done enough to get a fair view of the cars consumption plus there will have been a few cold starts over that period.

Ive just filled it up so I will be checking the consumtion by the tank to make comparisons with the computer.

I have a couple of questions-

Firstly, how is the MPG calculated? Is it an average of the previous 5 miles consumption or so (like my old SAAB), or is a much shorter distance or for that matter instantaneous?

And secondly, Is there any particular fault that would increase fuel consumption that I should be checking for?

The cars got 47/48k FSH tyre pressures good, but the car is admittedly due a service. The air filter is however very clean on face value and the car is running very well, no smoke etc.

Well after a couple of thousand miles I know realise that the MPG is calculated from the last trip meter reset, handy having a trip A and B. Unfortunately i'm only getting low to mid thirties in town and low forties on a decent run. I guess that has a lot to do with my driving style and the amount of weight I carried on the only long run ive been on (6up plus luggage).

 

[larkim]

Does anyone know if Fiat have been "officially" written to about this cockup? You'd have thought that it was in their interest to have the consumption readout "accurate" (I'd have expected it to under-estimate consumption, if anything at all).

As an aside, I've just got a brand new 1.9 Multijet. Only done 2,500 miles so far, but I'm getting only just over 40mpg brim to brim (read out says about 33.5 - 34). I'm not too impressed with that. Neither myself or the wife are particularly heavy footed with the Multi, and at least 600 of those miles have been nice long runs on the motorway at a normal cruising speed. I don't cruise at 60-65 mph, though; I've not owned a diesel before, so is that a more "recommended" speed for fuel efficiency? The brochure (for what its worth) shows 34.4 to 50.4 as the "range" of MPG, so I suppose I am within that.

Matt

 

[missionary]

Larkim wrote...
Only done 2,500 miles so far, but I'm getting only just over 40mpg brim to brim (read out says about 33.5 - 34). I'm not too impressed with that. SNIP

But its a new car - all the cars I have had since 1966 have never given good mpg until well run in. The engine and transmission have to be nice and loose before you can expect a good return.

As for the computer's calculation in USG, I am not really bothered as a brim to brim calculation is always going to be better than any electronic figure. At times we have to be a bit old fashioned ! Don't fret, it will come in time.

cheers
mish

 

[MikeGipson]

Hi Mulipla Forumists.

How accurate do you consider the MPG readout of your Multi?

Has anyone out there been exacting enough to compare the readout with a reasonably scientific series of brim-2-brim checks?

I have just fitted the roofbars & roofboot prior to the holiday trip. Driving around the M25 a couple of times (rush hour, but fairly easy traffic) I'm reading 50.2 mpg (JTD 110).

I don't expect such good figures when we hitch up & tow.

What are your experiences?

Yes seems to read around 80% of actual consumption - got a Multijet 120 Eleganza

 

[jcc]

Having just got a 2004/04 JTD115 with the trip computer, it seems to read about 35MPG, which I thought very disappointing, until reading the thread.

This is my second Multipla, having run a 2000W JTD105 from new for three years (which didn't have the computer). This always seemed to return 40MPG even when thrashed, which was most of the time.

so I will ignore the MPG figures from now on, and go back to the tried and tested method of checking the mileage and fuel put in the thing!

 

[tomo28]

Hi ,

im interested that someone posted that their trip computer has under read the MPG !! my experience is over reading !!

i posted a while back about the website WhatMPG where im collecting real world MPG information. Alot of Fiat owners posted so thx to them. If you havent posted yet please do to share info with all. Below is the real world MPG figures visitors have submitted so far (most economical first)

Model engine year MPG
==================================



Panda
1248cc multijet 2006 64 Punto Active 1.2 petrol 2003 53 grand punto 1200 2006 52 Punto Active Sport 1.2 2004 51 cinquecento 1.2 1995 50 500 Lounge 1.2 petrol 2008 50 Punto 1242cc 2005 49 Punto Sporting 1.2 16 valve 2000 47 punto 1.2 16v 2000 45 Punto 1.2 2003 45 Punto 1.2 2003 45 500 1.2 2008 44 Grande Punto 1.9 diesel 2007 43 Grande Punto 1900 2007 43 Doblo 1.9D 2001 42 grande puntp 1.9 2007 42 seicento 1.1 2000 40 doblo 1.9jtd 105bhp 2006 40 bravo 1250 2000 40 Grande Punto 1.2 2006 37 seicento 1108 1998 33 bravo active 1.4 2007 32 uno turbo i.e. 13.01 1988 30 Bravo 1.8 1994 30 Marea 2 1997 30 Abarth Punto SS 1368 2008 28

 

[jcc]

Done a few miles in it now - consumption as measured by me is in the low 40s, as expected . the readout varies between 36 and 41.

 

[rushthedj]

Hi All,

I've been logging the consumption on my 2000 1.6i ELX for a while now and have been seeing the same discrepancy you all have. However, I've just noticed by looking at the distances I've been driving on Google Maps for my last couple of runs that the trip meter seems to be over-reading distance travelled by around 10%. Is anyone else seeing this? If I use the reduced trip distance to work out MPG it agrees fairly well with the computer read-out (though I don't think we can ever expect perfection as I was once told that the computer readouts are generally not based on actual fuel pumped to the engine, they're based on ECU fuel flow maps pre-programmed at the factory. Anyone know more about that?).

I'm not sure if the total mileage travelled is over-reading, I'll start logging this now so I'll know more after I've refueled a couple more times in a few weeks (I don't drive much at the moment).

Can anybody else confirm/rule this out?

Cheers,
Rory

 

[DORSETVDUBSTER]

I haven't looked yet as it's my wifes car but where do you find your indicated MPG?

Any info appreciated!

 

[Pandabloke]

I haven't looked yet as it's my wifes car but where do you find your indicated MPG?

Any info appreciated!

Scroll through the menu with one of the two right hand buttons on the speedo. The top one I think. Can't think straight, on the Caffreys!

 

[larkim]

However, I've just noticed by looking at the distances I've been driving on Google Maps for my last couple of runs that the trip meter seems to be over-reading distance travelled by around 10%. Is anyone else seeing this?

[Snipped]

I'm not sure if the total mileage travelled is over-reading, I'll start logging this now so I'll know more after I've refueled a couple more times in a few weeks (I don't drive much at the moment).

Can anybody else confirm/rule this out?

Cheers,
Rory

I had a similar thought, but I put a handheld GPS in the car for a few good long journeys and the reading on the trip meter was almost spot on with the GPS tracked journey. It would, of course, be highly sensitive to different tyre pressures etc which could be affected by temperature or under / over inflation.

Next time I take the multi in for a service I'm going to put it on the list of warranty repairs, and see what answer I get from them about why it is wrong!

Matt

 

[lj2307]

We have just bought our multi and it was advertised as doing 55mpg by the previous owner but we put £10 of diesel in and only got 47miles out of it so that means we got around 23 mpg I dont put my foot down alot either because im concious of the fuel consumption.

Lisa

 

[Shepherd]

I raised this issue on the forum a few years ago when I first got my JTD. The MPG reading on mine always seems to be about 20% under.

 

[demag]

I checked the last two tankfuls brim to brim and got 42.5 and 42. Both mixed driving heavy traffic stop start and some motorway and A roads. Computer on car said 34!!! Which is about 20% ish. Amazing isn't it.

I'm glad I'm getting 20% more than the other way round!

 

[taxiadam]

I have a X reg 105 ELX diesel.
37.85mpg

Sad I know but I have kept all my fuel receipts from when I bought the car back in December. This figure takes in having kayaks on the roof, bike rack, motorway driving, driving like a maniac etc (not all at the same time by the way!!)

8648 miles, £1000.24 on fuel, 1038.64 litres of fuel, 228.468 gallons

 

[multieddie]

I'm getting a reading of around 40mpg with a mixture of motorway and city driving, dropping to around 36mpg on urban only. I'm not particularly lead-footed and stick to around 60mph on the motorway.

On a recent drive from Liverpool to Hereford (90% motorway got an overall reading of 48mpg).

I think it is an average rather than an on the fly reading. The longer you leave it without resetting, the less it fluctuates, which would tend to support the notion that it is and average.

 

[Pandabloke]

I'm getting an average of 41mpg through 25 tanks of diesel. This is brim to brim. Don't even bother looking at the computer anymore.

Interestingly, I just had the alloys resprayed under warranty, and drove it for a week after it was returned without checking the tyre pressures (it was also very hot and I used the aircon a lot!). When I next filled up I checked the tyre pressures and they were all nearly 1 bar down in pressure.

On checking my mpg on this tankful it was 37 mpg, the lowest ever and something of an anomaly. Curious how much difference low tyre pressures (along with aircon usage?) can make.

Needless to say that the mpg looks much better on this tankful.

It does appear that nosejob Multi's have a smaller fuel tank than uglybugs. I used to get 600 miles from the uglybug but struggle for 500 in the nosejob but get similar mpg's. And (obviously) I get noticeably less fuel into the tank, from virtually empty, in the nosejob.

 

[IanC123]

Hi. It's really interesting reading the different MPGs everyone has been getting. Not done a brim to brim on my Multi (02 1.9 JTD 115ELX) but have been checking the computer readings for some time now.

Had the car for about 4 years now and experienced all the routine multi problems. Leaking sun roofs, broken spare tyre winch, faulty brake disc sensor, rear wiper failure, 2 safety recalls - front springs and handbrake cable fouling, faulty clockspring, indicator wont turn off........ then to top it all a snapped cam belt (my fault as missed the recommended replacement by about 10k miles - although should have done it at 50k really). Anyways - still love the car.

Sorry - getting back to MPG. Before the cam belt snapped I was getting about 36 mpg on the computer - this involved mostly mixed runs of about town / country and motorway driving.

After the cam belt snapped I had the car repaired at a local garage rather than a main dealer as I didn't want to take out another mortgage. Agreed the price up front after the head had been lifted to look at the damage - £500 all in which I thought was a fair price considering a number of the valves obviously needed replacing and all the other parts - belt kit / tensioner / hyd lifters. When I got the car back it was running at about 33 mpg on the computer. I figured that the damage to the engine had obviously caused the poorer fuel consumption figures.

A month or so ago I put the car in to the same local garage for a full service - new oil / air / fuel filters etc. The car is now doing between 39 and 44 mpg which is the best it's ever done so can't really complain. Reading this post it may actually be doing better if the computer is about 10% under.

Interested to know what other users have found to be the best fuel / tyre pressure etc to get the best mpg - I've tried total garage excellium diesel which claims to give you 30 miles more per tank but can't say I've really noticed the difference to be honest?

 

[SPONGEBOBMAIDENPANTS]

Our 06 JTD seems to do 40-43mpgWhich is a almost all b road and a little town city driving.I am happy enough with thatOf course with the wife blasting out the climate control in this heat it won't be so good this tank full