A couple of previous threads on this subject appear to be dead and buried, so I thought I'd dig it up again. The thread I have in mind posed the question as to whether supermarket fuels were worse than premium brands. I tried a little experiment whereby I'd would fill up alternatively with Sainsbury and BP Ultimate diesel. I tried to be objective about this but not being very scientific by nature it didn't quite work out as I'd planned, however, here is what I found. I also tried to make a note of the type of driving and not only the trip computer readings but also worked it out manually (alright, on a calculator) after brimming the tank. At this point the tank was full of Sainsbury's diesel.
03/09/07 Sainsbury's. Trip:56.5 mpg. Actual:61.5mpg. Mostly m/way
with a leisurely trip to Llangollen (100 miles approx - 3 up)
14/09/07 Sainsbury's. Trip:59.3 mpg. Actual:68.4mpg. Almost all rural national
speed limit single and dual carriageways. 487 miles.
28/09/07 BP Ultimate. Trip:52.7 mpg. Actual:53.5mpg. Almost all 17 mile each
way m/way commute. 375 miles.
11/10/07 Sainsbury's. Trip:53.3 mpg. Actual:64.8mpg. Almost all 17 mile each
way m/way commute. 404 miles.
30/10/07 BP Ultimate. Trip:53.3 mpg. Actual:56.3mpg. Almost all 17 mile each
way m/way commute. Forgot to note mileage.
Two things stood out from this little exercise. The first being that the kind of road I drove on was more important than the type of fuel in the tank and the second is how different the mpg fuel figures were depending on whether I used the trip computer or worked them out with a calculator. It does seem bizarre though that fuel figures should vary so much from car to car and even tank by tank on very similar journeys. Overall though, on BP Ultimate, the average consumption was 54.9mpg and on Sainsbury's it was 66.6mpg. This comparison was based on actual fuel figures not those derived from the trip computer.

The Beard said:

Overall though, on BP Ultimate, the average consumption was 54.9mpg and on Sainsbury's it was 66.6mpg..

Click to expand...

That's a massive gap, but I've found that BP Ultimate gives by far the poorest MPG returns. It also IME makes the Panda sound like a tractor. I now avoid it in favour of ordinary BP. Perhaps I should head over to Sainsburys...
My Panda is now very consistent MPG wise on ordinary BP: on my mix of largely rural and semi-rural running trips of between 5 and 25 miles one way, driven normally (not exceeding speed limits, but also not trying for economy by coasting etc), it delivers between 57 and 59mpg actual.

Barry

In the Multipla section we found the fuel computer was way out as well.
It worked out perfect if we used American gallons which are about 5% different in size.

See here:
https://www.fiatforum.com/multipla/36821-accuracy-mpg-readout.html

maybe it is american software

My 1.2 Dynamic returns a consistant 4mpg more with brand name fuel against the supermarket stuff?
It is more responsive also, even the wife notice's it!!!!!
Must be a petrol thing.
If you want max mpg with a diesel, just use red, it is better grade, and returns more mpg. Not me though, i only have petrol vehicles, look elsewhere Mr Excise.

There is a TV programme on satelite/cable called "Mythbusters". For the benefit of anyone who hasn't seen it, viewers write in with requests to either prove or disprove certain popular urban myths, which frequently results in things being blown-up. In one programme they were asked to answer the question as to whether a car was more economical with the air conditioning on or the windows open to provide cooling. Using the car's trip computer the air conditioning was slightly more economical at about 16 m.p.g. (The cars were 2 big (read huge) Ford 4X4s, possibly Excursions or F150s. When they tried the test again, this time after draining the tanks and pouring in exactly one gallon per vehicle, the results were reversed, but what I thought was interesting (I know, I live a really boring life) was that the consumption figures were over 20% better than when taken from the trip computer. The explanation given was that the readings were taken from the air flow meter, not the petrol passing through the injectors, and were, in fact, a mathematical calculation.

Hmmm, my 1.2 dualogic has just reached 1,000 on the clock so obviously still running in,
the comp tells me I am averaging 49.7 mpg but in reality I think its lower, I am just now starting to watch how far I can travel on a full tank, I am using Tesco petrol which I reckon is as bad as it gets but the Tesco points over the year send us on a nice holiday abroad

As an experiment, in light of the differences I have encountered between what the trip computer tells me and what I have worked out with a calculator, I was wondering if anyone could do the same as me and fill the tank, reset the trip meter and then at the next fill up make a note of the amount of derv it takes, the mileage, the trip meter reading and work out the true mpg figure on a calculator. I know it sounds a bit sad, (ok,very sad), but I'd be interested to know if trip computers in general are as inaccurate as mine when it comes to mpg figures and if so what about average speed and does this mean the digital mileometer is also inaccurate? Er...this is starting to sound like I don't have any friends. Oh all right, I don't have any friends but I'd still be interested to know if anybody else's car will actually return better mpg than the trip computer tells them.

Auto Express have done some actual on road tests & the Panda results altho top of the list are way down to the expected results from owners


Want to save fuel and cut down your CO2 emissions? The DTI has just unveiled the “Act On CO2” initiative to encourage car buyers to purchase more fuel-efficient motors. Auto Express has conducted its own research to find Britain’s 100 most economical motors.
The tests were conducted on public roads and take into account traffic conditions, weather, types of road and all the other variables that influence your mpg. Ten classes of cars were tested, from city cars to SUVs and family saloons to MPVs.
Best sector of them all for economy – and also home to the cleanest motors in our test, was the city car class. The winner, and the most economical car we’ve ever tested, was the Fiat Panda 1.3 Multijet which achieved 52.2mpg. With few diesel engined city cars available only one other oil-burner made it into our top ten – the second placed Citroen C2 1.4 HDi. Best petrol was another Citroen, the C1 1.0 averaging 46.9mpg.

Make/Model Tested MPG
CO2 1. Fiat Panda 1.3 Multijet 52.2
114 2. Citroen C2 1.4 HDi 48.1

107 3. Citroen C1 1.0 46.9
109 4. Toyota Aygo 1.0 46.7
109 5. Peugeot 107 1.0 46.5
109 6. Kia Picanto 1.1 44.1
124 7. Daihatsu Sirion 1.0 42.5
118 8. Smart ForTwo 700cc 40.0
113 9. Fiat Panda 1.2 37.6
133 10. Ford Ka 1.3 35.7

147
Top 100 most fuel-efficient cars | Auto Express News | News | Auto Express

How come the diesel Panda gets 52.2mpg, and releases 114g of carbon per kilometre, when the Peugeot 107 gets only 46.5mpg, but releases only 109g/km? I thought carbon(fuel)+oxygen(in the air)=carbon dioxide. So the amount of fuel used should affect the amount of CO2 produced, surely? How can the Pug burn more fuel, but create less CO2? What am I missing?

Odd one that. As diesels of comparable size tend to put our less CO2 than petrol engines I would have expected the Panda to put out less CO2 than the Citroen. I seem to remember that the GLC has put the Panda MJT as well as the Citroen 1.4 hdi on their list of vehicles that would be exempt from the congestion charge. If this is true, I would be interested in seeing whether the Citroen with the petrol engine is also on the list.

Er...please disregard my last reply. I didn't read izzy's entry properly.

Some of you will be familiar with my Jan 05 MJ - has 65,000 miles to date and is still giving the following MPG (fill the tank, check the milage) over the last three fills:

63.2, 59.7 62.6

This is mostly twisty B roads (50/60 MPH = fun) with some motorway driving (75 ish but boring)

Look after them (Servicing etc) and they will repay you.

BTW, has anybody else out there got middle to high milage on their MJ?

My warranty is up ( 4 years OR 100,00Kms) and I am considering changing it in March or April. Has anybody else got to thinking that the bills for repairs (none worth talking about to date thankfully) will be the owners now, not the garage??

PS Will be buying another MJ

BJ20