A8 Parts Forum  

Go Back   A8 Parts Forum > A8 D2 > D2 - Fuel and Exhausts

D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

Reply
 
Thread Tools Display Modes
  #1  
Old 26th May 2017, 11:15 PM
Goran's Avatar
Goran Goran is offline
Senior Member
 
Join Date: Feb 2011
Posts: 2,176
Default Fuel consumption report

I went to France for 3 days, just wanted to note down my fuel consumption for future reference.
Covered 1349km or 838.4 miles, used up 139l of fuel.
Thats 6.03 miles per litre or 27.4mpg. Worse than before.

The fuel figure was derived from fuel put in, full tank at start + 60l along the way minus remaining fuel which was 4l from VCDS but as I now know there are roughly another 7l in there when it reads 0. So estimated 11l remain in the tank.
Reply With Quote
  #2  
Old 27th May 2017, 03:11 PM
Regulus Regulus is offline
Senior Member
 
Join Date: Apr 2017
Location: Varmland, Karlstad region, Sweden
Posts: 484
Default

As you have calculated that the mpg is lower than before, after a long trip abroad. My initial thought would be that France use a different fuel mix.
Do you know how it compares to UK? There could very well be a different percentage of biofuel or ethanol in the mix.

I usually buy fuel in Norway as it has better milage, compared to Sweden. That goes for petrol as well as diesel.
__________________

Johannes
_________
Audi S8 -99, Pearlescent, Alcantara/silk napa leather, Burr walnut insert, Alcantara roof lining upper pack
A8 32V engine
-----
Jeep Grand Cherokee -98
Reply With Quote
  #3  
Old 27th May 2017, 07:57 PM
Goran's Avatar
Goran Goran is offline
Senior Member
 
Join Date: Feb 2011
Posts: 2,176
Default

Interesting observation, I never thought about the fuel difference.
I only bought 60 litres in France, 90 litres I brought with me from the UK.
Could be a number of other factors, new exhaust, errors in my previous calculation.
Reply With Quote
  #4  
Old 27th May 2017, 08:28 PM
The_Laird's Avatar
The_Laird The_Laird is offline
Senior Member
 
Join Date: Jun 2009
Location: Redmile: Leics, Notts, Lincs border - near Belvoir Castle
Posts: 5,069
Default

Quote:
Originally Posted by Goran View Post
I went to France for 3 days, just wanted to note down my fuel consumption for future reference.
Covered 1349km or 838.4 miles, used up 139l of fuel.
Thats 6.03 miles per litre or 27.4mpg. Worse than before.

The fuel figure was derived from fuel put in, full tank at start + 60l along the way minus remaining fuel which was 4l from VCDS but as I now know there are roughly another 7l in there when it reads 0. So estimated 11l remain in the tank.
You'll never get an accurate fuel consumption figure if you use "roughly" and "estimated" values. The only way to do it is to zero the miles before the trip when you fill the tank. Then keep filling the tank and setting the miles to zero, noting the miles each time. And the end of the trip, fill up and note the miles. I've been doing this on every tankful for years (I know I need to get out more!).
__________________
2002 Final Edition S8. Ebony black with Silver Grey leather and myrtle wood trim.
Current mods: solar sun roof, 20mm rear spacers, 15 mm on front, red brembo callipers, 6k headlights, rear view camera, engine remap, alloy dash dial rings, alloy navi rings, tt/phaeton pedal upgrade, (and custom matching foot rest) dension ipod interface & parrot hands free kit (both fully hidden), av input, tv in motion switched thro' PF switch in blanking plug right of steering column, Audi 'quattro' sill covers, repositioned centre console switches, radio clock, .
Planned mods: auto-dimming rear view mirror, dash cam (as steamship's), fit the ski hatch, refit philips drl's (or maybe not - nope, definitely not - horrible botch!).
Reply With Quote
  #5  
Old 27th May 2017, 08:40 PM
Regulus Regulus is offline
Senior Member
 
Join Date: Apr 2017
Location: Varmland, Karlstad region, Sweden
Posts: 484
Default

Quote:
Originally Posted by The_Laird View Post
You'll never get an accurate fuel consumption figure if you use "roughly" and "estimated" values. The only way to do it is to zero the miles before the trip when you fill the tank. Then keep filling the tank and setting the miles to zero, noting the miles each time. And the end of the trip, fill up and note the miles. I've been doing this on every tankful for years (I know I need to get out more!).
I second that
I keep a driver's journal since April 2001

edit: another advantage you will have is you can calculate the total cost per mile over time.
I discovered that my BMW 530D -99 in fact was basically as expensive to drive as my Jeep Grand Cherokee 5.2 -96. Despite the Jeep being twice as expensive on the fuel
__________________

Johannes
_________
Audi S8 -99, Pearlescent, Alcantara/silk napa leather, Burr walnut insert, Alcantara roof lining upper pack
A8 32V engine
-----
Jeep Grand Cherokee -98

Last edited by Regulus; 27th May 2017 at 08:48 PM.
Reply With Quote
  #6  
Old 27th May 2017, 10:13 PM
Goran's Avatar
Goran Goran is offline
Senior Member
 
Join Date: Feb 2011
Posts: 2,176
Default

Quote:
Originally Posted by The_Laird View Post
You'll never get an accurate fuel consumption figure if you use "roughly" and "estimated" values. The only way to do it is to zero the miles before the trip when you fill the tank. Then keep filling the tank and setting the miles to zero, noting the miles each time. And the end of the trip, fill up and note the miles. I've been doing this on every tankful for years (I know I need to get out more!).
That's exactly what I did. Filled the tank, zeroed the miles.
Then kept receipts of every fill up. Then VCDS'ed the litres remaining at the end of the trip. As per my first post.
The only error in the calculation, as I already said, is that we cant measure precisely the litres remaining when VCDS measuring block reads 0 litrs, but we know some fuel remains because when I filled the tank I only managed to put 87l back in. (I was not willing to fill the tank to full after the trip just to get a more accurate measure how many were left)

The problem arises is that VCDS will carry on reading 0l even if you use some of those 7l below zero.

So the error in my calculation is assuming that there are another 7litres below zero when VCDS reads 4l remaining.


Even this margin of error +/- 7l is not enough to account for my previous best mileage, which was 581 miles with VCDS reading 1 litre remaining.
But those were different roads than the trip to France, that could explain some of the difference.

Last edited by Goran; 27th May 2017 at 10:19 PM.
Reply With Quote
  #7  
Old 31st May 2017, 10:41 PM
Nick Jones Nick Jones is offline
Senior Member
 
Join Date: May 2015
Location: South Somerset, UK
Posts: 195
Default

Alot of French fuel is E10 these days and this IS enough to affect fuel consumption for the worse.

I understand that the actual brews vary over the year too.

Nick
Reply With Quote
  #8  
Old 2nd June 2017, 08:33 AM
Goran's Avatar
Goran Goran is offline
Senior Member
 
Join Date: Feb 2011
Posts: 2,176
Default

I filled 24l with BP 97 and 36l with Shell Vpower, those should not vary too much even in France surely?
I still think its to do with the exhaust, especially considering original exhaust was partially blocked with broken cat.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 09:33 PM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.