Lying Cars (Dash vs Reality)

Lying Cars (Dash vs Reality)

Author
Discussion

DickP

Original Poster:

1,117 posts

149 months

Saturday 3rd October 2015
quotequote all
My company car claims on the dashboard that it is averaging around 55mpg, and has said approximately this since I got it earlier in the year.

I thought though it would be good to just check what it actually is doing to see its accuracy. I presumed a slight variance may happen of a couple mpg. Reality is the car averages betweeen 46 and 47 mpg. That's a difference of over 10%! I guess I was naive to think that the car would be able to produce a genuine figure? Are lots of manufacturers playing this game as well, fooling their buyers into thinking the car is doing better than it really is?

poing

8,743 posts

199 months

Saturday 3rd October 2015
quotequote all
Mine seems to be about 3mpg out so somewhere less than 10% difference, probably about the same as the speedo over reads. I imagine that's not entirely coincidental.

eldar

21,614 posts

195 months

Saturday 3rd October 2015
quotequote all
DickP said:
My company car claims on the dashboard that it is averaging around 55mpg, and has said approximately this since I got it earlier in the year.

I thought though it would be good to just check what it actually is doing to see its accuracy. I presumed a slight variance may happen of a couple mpg. Reality is the car averages betweeen 46 and 47 mpg. That's a difference of over 10%! I guess I was naive to think that the car would be able to produce a genuine figure? Are lots of manufacturers playing this game as well, fooling their buyers into thinking the car is doing better than it really is?
I suspect they are almost always overoptimistic. My old BMW used to have a correction factor you could type in to make it accurate.

Slow

6,973 posts

136 months

Saturday 3rd October 2015
quotequote all
Speedo over reads by 10% mpg is out by 10% too. Guess it's a trick to make me think it's economical to drive a big 4x4 haha

J4CKO

41,287 posts

199 months

Saturday 3rd October 2015
quotequote all
350Z display just says "NOM NOM NOM, FEED ME bh"

DickP

Original Poster:

1,117 posts

149 months

Saturday 3rd October 2015
quotequote all
I can understand up to 10% for speedo variances etc. but more than 10% seems a bit bad for manufactures to be playing at...

J4CKO said:
350Z display just says "NOM NOM NOM, FEED ME bh"
laugh

bitchstewie

50,787 posts

209 months

Saturday 3rd October 2015
quotequote all
Are you going off a long term average?

My Golf lets me do "journey" "since refuel" and "long term" and I'm one of those sad gits who brims it, zeros the counter, then goes home and plumbs it all into a spreadsheet and it's almost always within 1-2mpg.

CaptainMorgan

1,454 posts

158 months

Saturday 3rd October 2015
quotequote all
My old Fabia vRS was 100% perfect, tested it over numerous different drives and conditions and every it was within 1mpg or so. Havent bothered checking the 320d as it's crap anyway (35mpg) and the Panda I've not had to put any fuel in yet lol.

poing

8,743 posts

199 months

Saturday 3rd October 2015
quotequote all
bhstewie said:
Are you going off a long term average?

My Golf lets me do "journey" "since refuel" and "long term" and I'm one of those sad gits who brims it, zeros the counter, then goes home and plumbs it all into a spreadsheet and it's almost always within 1-2mpg.
Spreadsheets? How 1996. You need an app, if for no other reason than to annoy the person behind you by taking even longer to reset and record everything wink

Crusoe

4,068 posts

230 months

Saturday 3rd October 2015
quotequote all
Does it not make a big difference how much you are stopped with the engine running, most only record on the computer when you are moving is stop start traffic, warming up etc. Will make it under read the actual fuel usage.

anonymous-user

53 months

Saturday 3rd October 2015
quotequote all
And how exactly are you recording how far you are driving between fill ups??

stevesingo

4,848 posts

221 months

Sunday 4th October 2015
quotequote all
On the wife's E90 BMW you can correct the OBC by going in to a hidden menu. Originally it was showing 27-28. when in reality it was doing 30-31mpg. Since changing the correction factor it is always within 0.5mpg when checked against the mile for a tank method.


bitchstewie

50,787 posts

209 months

Sunday 4th October 2015
quotequote all
poing said:
Spreadsheets? How 1996. You need an app, if for no other reason than to annoy the person behind you by taking even longer to reset and record everything wink
I work in IT and honestly, there are times when I see things and simply think "why?" and apps like Fuelly are one of those times.

I don't get the benefit tbh, assuming a single car and I just want to know my MPG and what it's cost me.

Tam_Mullen

2,280 posts

171 months

Sunday 4th October 2015
quotequote all
The trip computer in my car says I regularly get about 55MPG and have been 60plus. The average MPG it shows is 52.

My tank to tank manual mpg is 43 usually.

And its a VW hehe

Debaser

5,665 posts

260 months

Sunday 4th October 2015
quotequote all
How do you work out what fuel economy you're actually getting?

Jasandjules

69,825 posts

228 months

Sunday 4th October 2015
quotequote all
Debaser said:
How do you work out what fuel economy you're actually getting?
Work out how many miles you have travelled (read the trip computer) and then divide that by the number of gallons of fuel you put in at the pump.....

Tam_Mullen

2,280 posts

171 months

Sunday 4th October 2015
quotequote all
Debaser said:
How do you work out what fuel economy you're actually getting?
Really?

Fill up (I just fill til the 1st click but whatever you do it has to be the same every time!)
Zero Trip meter
Drive around
Refill
Litres/gallons(4.54 litres per gallon I use) then miles/gallons.


Simple smile

bitchstewie

50,787 posts

209 months

Sunday 4th October 2015
quotequote all
Debaser said:
How do you work out what fuel economy you're actually getting?
I have a spreadsheet and keep my receipts. I always brim the tank and make a note of the miles I've had since the last fill up - plug in the numbers and it spits out MPG and cost per mile.

Krikkit

26,500 posts

180 months

Sunday 4th October 2015
quotequote all
bhstewie said:
poing said:
Spreadsheets? How 1996. You need an app, if for no other reason than to annoy the person behind you by taking even longer to reset and record everything wink
I work in IT and honestly, there are times when I see things and simply think "why?" and apps like Fuelly are one of those times.

I don't get the benefit tbh, assuming a single car and I just want to know my MPG and what it's cost me.
You don't get the convenience of having a mobile spreadsheet that works out your mpg for you and makes pretty pictures?

When you say you work in IT... Are you an Oracle dbadmin who sits in a cupboard all day?

bitchstewie

50,787 posts

209 months

Sunday 4th October 2015
quotequote all
Krikkit said:
You don't get the convenience of having a mobile spreadsheet that works out your mpg for you and makes pretty pictures?

When you say you work in IT... Are you an Oracle dbadmin who sits in a cupboard all day?
Google Docs is a mobile spreadsheet smile