I believe it is very much how you drive that has the biggest effect on fuel economy.
This week I drove from Bracknell to the outskirts of Cardiff at 60 mainly on cruise control and my petrol auto CRV did 43.84 MPG on my return trip I drove as uneconomically as I could with a heavy right foot and got 24.37 MPG.
|
I believe it is very much how you drive that has the biggest effect on fuel economy.
I agree. My commute is mostly A- and B- roads, every few weekends I travel 200 miles round trip to visit family. My shoddy old 1.8 Escort has a combing figure of 36mpg, if I thrash it on the commute the brim-to-brim figure can be as low as 30mpg, but if I drive gently all week it approaches 40mpg. The motorway journey gives me 43mpg at 60-65mph but again down to 30mpg at 90-100mph. It depends how badly I want to get home to bed on a Sunday night.
Dave TD
|
|
|
I believe it is very much how you drive that has the biggest effect on fuel economy.
I agree. The method of calculation has the next biggest effect. I don't place any credence on figues calculated on any basis other than an average over a reasonable length of time ~ say a month or 1000 miles minimum. Even then, the season/weather can have a big effect.
Edited by L'escargot on 29/06/2009 at 08:42
|
There are too many variables.
It could be different fuel, driving style slightly different, more traffic, weather, car tyres, car mileage (it was new 10 months ago so how many) etc.
Any of these could affect the consumption.
No two cars, even if identical, will be the same.
|
|
Are these MPG figures from the car's computer, or your brim-to-brim calcs?
|
|
|
|
|
|
Granted---But where the heck is it???
|
|
On the left, just above the top thread.
|
|
|
Granted---But where the heck is it???
You have email. DD, BR Moderator.
|
I would guess that the newer car has a particulate filter, which in my experience has a negative effect on fuel economy.
My Citroen C5 diesel (with particulate filter) averages around 38mpg. My previous C5 had no particulate filter, and averaged 43mpg (or 51 with the wife driving).
|
I would guess that the newer car has a particulate filter, which in my experience has a negative effect on fuel economy.
As I pointed out a few weeks ago, the 207 manual gives consumptions for identical models with and without a FAP, suggesting that its adverse effect on consumption is about 10%.
But does the OP mean a 'duplicate car' or an updated version? If duplicate, why change?
Edited by Andrew-T on 27/06/2009 at 11:01
|
OP needs to approach this methodically.
First of all are the two cars actually identical. Several versions of the HDi engine have been used in the Picasso 1.6 and 2.0 and (IIRC) in 90 and 110PS versions. FAP and transmission differences add further scope for variation.
Are the journies exactly the same or have you changed work sites, routes time of travel etc. The HDi is pretty good in urban traffic but the difference between pre/after school run and commute times and travellling at 08:15 could be significant.
FWIW my 2000 Xantia HDi 110 averaged 47 pretty much whatever I did with it.
|
|
Both cars 110bhp diesels with FAP. Nobody on site has brought in the question of the 5%biodiesel now included in our derv????
|
|
The difference between your measured 47mpg and 50mpg is less than 10%. That could easily get lost in differences in speedo/ mileometer accuracy between the 2 cars.
|
Whilst most common figure for new car is 47mpg, the most common figure for old one was 54mpg. But here is a quizzler for you. On the two occassions that new car did 50/50+mpg it was filled up at an Asda store. Two of the worst tankfulls were returned after fuelling up at a different Asda store??? A company called Harvest Energy are supposed to supply Asda with road fuels, but won't confirm it to me. However, during the last fuel strike, some supermarkets were getting fuel. This fuel was imported as fuel, not crude oil. I strongly suspect, but can't prove, that the "Good MPG from Asda" came from a load of imported fuel, not subject to the stupid UK Govt's 5% biodiesel additive. The poor returns were from Asda and Shell fuels refined in the UK.
I would be very interested to hear from people running diesel cars manufactured after 2004, to see if they noticed an increase in fuel consumption from summer 2008 till present. Cars with the HDI type of engine are most likely to have noticed this, and include Ford, Volvo, Mazda Pugs and Cits.
Renault, on the other hand, have contacted all their new diesel car customers and warned them not to use any form of biodiesel, exceeding 30%vegetable oil additive.
This would render their engine warranty void.
As far as transmittion is concerned, i was not advised by the garage that there may be a difference, and the driveability feels the same. OK-I was yet another mug to buy from snip.
Please don't name & shame - Webmaster
Edited by Webmaster on 27/06/2009 at 20:58
|
2005 & 2008 - different ecu updates maybe?
I don't think the 5% biodiesel would make that much of a difference.
Edited by Shaz {p} on 27/06/2009 at 19:59
|
Yes, Shaz(P), the first time i complained about fuel usage they took car in and supposedly added the latest ECU update. NO difference. On other websites there are haircurling stories about biodiesel/veg oil.
I shall be writing a piece about it when certain confirmations come through. Govt. have been told to abandon this dictate in the meantime.
|
I strongly suspect that the "Good MPG from Asda" came from a load of imported fuel ...
My natural assuumption is that Asda sites are just as likely to sell identical fuel as they are to dispense it in identical quantities. Although Trading Standards keep tabs on the accuracy of sellers' pumps, there was a place in South Wales in the last few months which had been selling significantly short for quite a while. It is unusual, but not unknown, for this to happen.
I doubt if the error could be 10% though.
|
These boys are big Andrew, dealing on world markets, so fuel can come from any source. Rumour has it that Derv is imported from Russia as well.
In regard to the 5% biodiesel additive, this is not a standard product. This weeks load may be made from rape seed oil, next weeks from sunflower oil, etc etc. The problem is that each oil has it's own properties which react differently in todays high tech engines.
|
The topic of fuel consumption is regularly done to death on here, and my conclusion is that it is usually hard to reach one. As Les has said, the only reliable measures are made over 1000 miles or more, which means that fluctuations due to different fuels, weather, driving habits, traffic conditions, etc. cannot be identified with certainty, even for the same vehicle. Comparisons between vehicles may be clear, but attributing them to anything in particular (or particulate) is just as tricky, IMHO.
And in this century I suspect many drivers accept the readout from their car's computer, without checking it in the 'traditional' way.
|
Tests carried out from 2500 mls to 6800mls, on a brim to brim basis. Most variables kept to minimum eg several fills from same pump. Cars computer is a waste of space.
Would expect slight variation between cars, but not this wide, nor such widely varying returns from this car. Diesel specialist says something needs investigating, but Citroen Uk won't do this under warranty, and say car is within their perameters. They refuse to tell me what these parameters are!!!!
|
|
|
|
|
