Trip computer lying!

Benjic2

Active Member
Aug 29, 2011
1,030
3
Right, I have noticed this ever since I had my car but I would like to know the reason for it now :)

Basically if I let it run low on fuel ( <5 miles ) then put £10 in, the trip computer reads 70 miles till empy ( Fair enough). However it will only do just 40 miles, so why does it lie to me! Surely it should take into account the average consumption and not just a random number. My average consumption over the last few thousand miles reads 30.1 mpg.

Maths:

£10 @ 1.40 a litre = 1.6 gallons of fuel which sound be 48 miles of fuel ( So pretty close to actual which means the average comsumption calculated by the car isn't that far off).

Therfore that suggests it doesnt take into account the actual consumption, which seems a pretty daft idea. For example, I will park up at night and the computer will read 20 miles, then I will start it in the morning and it will immediatly go to 5 miles range. Stupid Seat!

Anyone else's the same?
 
Nov 27, 2006
1,204
1
www.cardomain.com
It's because your fuel economy on a warm engine at night (and the last figure it calculated as you rolled up to the pump) is considerably better than full-choke, cold starting in the morning.

If you drive uphill, under load, your range will drop...cos it assumes you'll be using the rest of your fuel at the same rate (it doesn't know how big the hill is) When you decend the hill, your consuption typically runs into the 100s (or ---) and your range will go up massively.
 

bigbadjay

Active Member
Jul 16, 2011
1,670
26
North Manchester
Mine read 240 at about the halfway mark. Disconnected battery. Connected again sometime later. Now reads 150 miles!!! It usually stays within 10 miles of the day before on cold startup
 

Deleted member 74601

Guest
Mine always under reads at the start of a tank (I fill it full), and then over reads near the end (under 30 miles or so).

The highest mine has ever said I can get out of a full tank is 640 miles. I regularly get around 800 miles.
 

Benjic2

Active Member
Aug 29, 2011
1,030
3
So It seems its not just my car that makes random numbers up then, at least that is good to know :cartman:

I don't know why it just doesnt use the trip 1 average MPG to work out the range though, my last car did this and it was always spot on. I have run the Leon 20 miles past the point where it reads "0 miles" too and it was still going...

It's because your fuel economy on a warm engine at night (and the last figure it calculated as you rolled up to the pump) is considerably better than full-choke, cold starting in the morning.

If you drive uphill, under load, your range will drop...cos it assumes you'll be using the rest of your fuel at the same rate (it doesn't know how big the hill is) When you decend the hill, your consuption typically runs into the 100s (or ---) and your range will go up massively.

Yeah but I dont even start the engine in the morning, just turn the ignition on and it has magically lost 15miles of fuel :confused: Maybe it anticipates a cold engine but either way it is confusing. My commute is 10 miles so when I park up I dont need to re fuel, but when I get in it in the morning, it decides it wants petrol and make me late for work. Moral of the story don't be a tight arse and just fill it up... off the the petrol station I go :D
 

DavidS

Active Member
Oct 17, 2012
119
0
Mine always under reads at the start of a tank (I fill it full), and then over reads near the end (under 30 miles or so).

The highest mine has ever said I can get out of a full tank is 640 miles. I regularly get around 800 miles.

800 miles per tank? Thats amazing! I have a PD170 and would never see 800 to a tank, I cant even break 50mpg on a 450mile motorway drive! Think i'm getting a raw deal.
 

t121anf

Newbie
May 14, 2004
570
9
800 miles per tank? Thats amazing! I have a PD170 and would never see 800 to a tank, I cant even break 50mpg on a 450mile motorway drive! Think i'm getting a raw deal.

same here, though not tried any long journeys yet, mine seems to average 40/45mpg
 

calvR

Active Member
Oct 21, 2011
392
2
Kent
I can leave the yard in the morning in my truck with a 600 mile range, travel 160 miles and stop with a higher range than i started with. So i believe it is normal to be calculated on current mpg
 

robdf2

Yellow is the best
Feb 21, 2006
3,605
2
location , location
I dont think it uses the average to calculate , it uses the instant mpg to calculate each journey , so you could say have 50 miles range left , but then have a spirited drive which eats into your instant mpg , if it was worked out on your average you would see it fall by 5 or 10 at worst.

well thats how i think it works anyway lol
 
Jan 31, 2011
511
1
ipswich/banbury
Right, I have noticed this ever since I had my car but I would like to know the reason for it now :)

Basically if I let it run low on fuel ( <5 miles ) then put £10 in, the trip computer reads 70 miles till empy ( Fair enough). However it will only do just 40 miles, so why does it lie to me! Surely it should take into account the average consumption and not just a random number. My average consumption over the last few thousand miles reads 30.1 mpg.

Maths:

£10 @ 1.40 a litre = 1.6 gallons of fuel which sound be 48 miles of fuel ( So pretty close to actual which means the average comsumption calculated by the car isn't that far off).

Therfore that suggests it doesnt take into account the actual consumption, which seems a pretty daft idea. For example, I will park up at night and the computer will read 20 miles, then I will start it in the morning and it will immediatly go to 5 miles range. Stupid Seat!

Anyone else's the same?

you a student or something? who puts a tenner in when empty? isn't it boring having to go to the petrol station all the time? I saw someone with a modded GT4 Celica pull into a petrol station the other month and he paid for his fuel in loose change to the princely sum on £6.54 which the way he was driving into the station would have probably just about got him to the other side of Ipswich.
 
Nov 27, 2006
1,204
1
www.cardomain.com
:p

Half a tank seems to last me about a week, and I'm always playing petrol-light bingo

The (consistently) cheapest Shell station around here just happens to be opposite the pub I go in on a Thursday night, so if I've run for a couple of days on the orange light I'll put maybe 20ltrs in instead of 15
 

Benjic2

Active Member
Aug 29, 2011
1,030
3
you a student or something? who puts a tenner in when empty? isn't it boring having to go to the petrol station all the time? I saw someone with a modded GT4 Celica pull into a petrol station the other month and he paid for his fuel in loose change to the princely sum on £6.54 which the way he was driving into the station would have probably just about got him to the other side of Ipswich.

Nope, I have 2 cars. My commute is just less than 10 miles and I don't ever use the Leon for it apart from the weekend so it would be silly to drive around with a full tank everywhere. £10 will easily last all week :) It was just this occasion that the leon was infront of my other on the drive so I had to use it for work.. that is when it lost 15miles overnight
 

joolsvern

The biggest MEMBER here
Jun 22, 2009
276
1
Doncaster
I walk to work as its about 10 metres away, in fact I have to walk further from my back door to the front gate than the front gate to work. Costs me 50p to pull car out and park up ready for when I need it though :D
 

Deleted member 74601

Guest
800 miles per tank? Thats amazing! I have a PD170 and would never see 800 to a tank, I cant even break 50mpg on a 450mile motorway drive! Think i'm getting a raw deal.

Yeah new CR engine with mostly motorway.

I do carry a lot of heavy gear though, equivalent to a full car, otherwise it would be better. My average has come down this winter though, getting more like 730-750.
 
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