Ok so here's the problem:

MPG over a week (mainly motorway driving with a steady but light-foot) shows typically 39-40 MPG on the trip computer (set to average). Ok, not great but then I did buy the T-Jet 150... my choice.

However, on filling up at the service station - measuring the number of liters used and the mileage covererd I'm actually geting approx. 35.5-36.5 MPG.

Does anyone else find that the trip computer is over-estimating the MPG ?

Now I do realise that the MPG is an estimate based on injector delivery, air-flow etc etc, and will be subject to numerical errors in integrating the consumed fuel with fixed point maths yada-yada, but even so, a repetable +10% error in the reading ?

I'm thinking I'm either looking at some kind of problem with the car or FIAT are applying a fudge-factor to the trip computer to make you think you're doing better than you really are.

(Bear in mind also that my light-footed MPG reading is still way off the 49.6MPG extra-urban figure quoted by FIAT, but then the engine is still pretty tight at just 4000 miles).

Steve.

Is that 49.6mpg downhill with the wind and coasting on 99 ron fuel ????? oh and low rolling resistance tyres


I have always thought the figures all manufactures quote are rubbish as they are tested under the best possible conditions etc etc and on a day to day basis you would not meet the same criteria and as such not get the figures stated.
but that is just my opinion, be it right or wrong.

And at 4k i would say you would not get your best economy until around the 10k mark. well at least that was true with my 500 ?

Will have to wait and see about the bravo, but im not getting past 25mpg!!!! at the moment

My average is about 34mpg over the 18 months I've had the car. If I was to drive the way I like to all the time, I think I'd be getting closer to 26mpg...and if I used the Sport button every time I consider it I think I'be down at about 20mpg!

The figures quoted in the handbook are bull...and I do admit to getting jealous when friends driving other marques quote mpg figures at me and how much they get from a tank...but then I remember...they're not driving a Bravo!

In my Panda the MPG gauge is always around 4-5 mpg over the top :bang:

So you are not alone !


Trev

Yeah i have the 500 for fuel economy 49.8mpg avg around town and if i ''sunday drive'' on the motorway's i get 55-57mpg avg.

Go to admit i didnt buy the bravo for fuel economy, if fact it was not a factor in the buying process at all. but again thats just me .

I have to say, I think the trip computer must be lying a tad, cause there's been days when Ive been cruising to work along the a45 in sixth getting.. 76mpg!!!

That can't be right!

Steve5665 said:

Ok so here's the problem:

MPG over a week (mainly motorway driving with a steady but light-foot) shows typically 39-40 MPG on the trip computer (set to average). Ok, not great but then I did buy the T-Jet 150... my choice.

However, on filling up at the service station - measuring the number of liters used and the mileage covererd I'm actually geting approx. 35.5-36.5 MPG.

Does anyone else find that the trip computer is over-estimating the MPG ?

Now I do realise that the MPG is an estimate based on injector delivery, air-flow etc etc, and will be subject to numerical errors in integrating the consumed fuel with fixed point maths yada-yada, but even so, a repetable +10% error in the reading ?

I'm thinking I'm either looking at some kind of problem with the car or FIAT are applying a fudge-factor to the trip computer to make you think you're doing better than you really are.

Click to expand...

Yes , it's way out.
On my 1.6 ECO it overreads by between 5 and 10% on each tankfull.
It's done that way to give you a warm happy glow when you see how economical your car is , but it's not true at all.

Most manufacturers do the same. On VAG cars it's possible to correct the trip computer with VAG-COM and make it more accurate - I don't know if anything similar is possible with a FIAT.

brav0 said:

I have to say, I think the trip computer must be lying a tad, cause there's been days when Ive been cruising to work along the a45 in sixth getting.. 76mpg!!!

That can't be right!

Click to expand...

Is that average or instant mpg

Omad said:

I have always thought the figures all manufactures quote are rubbish as they are tested under the best possible conditions etc etc and on a day to day basis you would not meet the same criteria and as such not get the figures stated.
but that is just my opinion, be it right or wrong.

Click to expand...

In my last two cars (both Skoda Octavias) I did get the manufacturers quoted figures. I do drive reasonably economically and do a fair amount of motorway mileage which is a factor though.

I've yet to get the quoted figures on my Bravo in the long term (though I have on a couple of tankfulls) but that's in part due to it trying to regenerate the DPF every 100 miles!

Once that's (hopefully) fixed I should get an improvement.

My average on the readout has been between 37 and 41 mpg. I reset it every week when I fill up. The amount of petrol I put in does not reflect this. I'd say it is overestimating by about 10%.

I also have a T-Jet 150 and the trip computer is pretty correct on long journeys.

However, it shows lower than actual when driving in city (with about 1l/100 - sorry for using modern measures here ) and I think there is a very good explanation about it. When you drive from a traffic light at 1st gear, the trip computer usually shows instant consumption of 25l/100. This is the max possible consumption it can show, as it is limited to 25l/100. However, we can easily assume that the car sometimes consumes more, let's say, 28l/100. The difference of 3l/100 is not taken into account by the trip computer when calculating the average consumption, because the limit is set to 25l/100. Voila!

If you manage to drive on first without getting to the limit of the instant consumption, I am pretty sure the average consumption will be correct.

my trip computer is WAY out.. its stupid.. just makes me think whats the point in even having a trip computer.. i managed to get my car to read 65mpg on average over a 154miles..

i think the actual was about 45mpg. Its shocking. im hoping when i get mine fixed as well i should see an improvement in fuel eco.

i bought the car with both speed and ECO in mind. Otherwise i wouldnt of went for a diesel.

im not completly dis satisfied with it though since my old car was doing around the same Mpg and was alot slower so least iv gained one thing without loosing out on the other..

Getting 35mpg in my last car would have been a dream. It was a ford cougar 2.0l and the trip always ended up at 26mpg

I will be happy if I can get 35mpg in my new bravo sport t150, my size 10 feet tend to be heavy

But as the guy above says i did not buy it for fuel economy, It seems people are only "living" these days not "living it up"

Do you all switch off your air conditioning to save fuel and melt to save a few pennies

That is instant Omad. My Average read's abuot 40-45

Charnwood Fox said:

My average on the readout has been between 37 and 41 mpg. I reset it every week when I fill up. The amount of petrol I put in does not reflect this. I'd say it is overestimating by about 10%.

Click to expand...

Pretty much exactly the same as mine...

Good to know I'm not alone. Like others have said I didn't buy the T-Jet 150 for fuel economy. My main concern was if this was indicative of an engine fault - seems not.

Steve.

My trip meter tells me that over the last 2522 miles, I've got an average fuel consumption of 50.5mpg.

Actual fuel put in over 2566 miles was 237.09 litres, which works out at 49.12mpg.

So thats about 2.8% difference. Seems fairly similar to the speedo error. How accurate are fuel pumps at garages? Do you get a little more for your money, because of fear of trading standards if the garage gives you short measure?

neilshep said:

My trip meter tells me that over the last 2522 miles, I've got an average fuel consumption of 50.5mpg.

Actual fuel put in over 2566 miles was 237.09 litres, which works out at 49.12mpg.

So thats about 2.8% difference. Seems fairly similar to the speedo error. How accurate are fuel pumps at garages? Do you get a little more for your money, because of fear of trading standards if the garage gives you short measure?

Click to expand...

That's as accurate as you are likely to get on any car I think.
A friend used to run a petrol station and he told me that the pumps were accurate to -0/+2% , so they can give you a smidge more than you paid for but not less.

Dr Zoidberg said:

That's as accurate as you are likely to get on any car I think.
A friend used to run a petrol station and he told me that the pumps were accurate to -0/+2% , so they can give you a smidge more than you paid for but not less.

Click to expand...

Does that go for BEER pumps as well?

neilshep said:

Does that go for BEER pumps as well?

Click to expand...

No but it applies to the glasses the beer is served in

Steve5665 said:

Pretty much exactly the same as mine...

Good to know I'm not alone. Like others have said I didn't buy the T-Jet 150 for fuel economy. My main concern was if this was indicative of an engine fault - seems not.

Steve.

Click to expand...

I don't think I drive to bad but I'm hovering around 29MPG in my 150 Tjet!!! I do give it a little blip now and again but usually I drive pretty well. I'm used to my old Rover 75 diesel - so probably have a bit of a heavy foot at the moment as I've only had the Tjet for about a month.

The wife's car is a diesel too so perhaps I'm driving it all wrong!?