Mpg readings

[andy2286]

Hi guys, I have a 1.4 tsi Octavia mk2 and when I reset the overall mpg readings (1 and 2) I seem to get two different readings from them. For example on my way to work today mpg reading 1 was reading 61mpg and mpg reading 2 was reading 54mpg. Can someone explain this to me please.

Also, I've heard the readings can be a little optimistic,  but how much? I'm a very keen eco-driver. 

[john999boy]

Do you mean that you've reset both the short and long term readings as resetting one won't alter the other? BTW there is a VCDS setting to adjust the 'error'.

[ian89]

as said one is long trip and this takes all your journeys into account the other is short trip and goes off your current/most recent journey 

[philbes]

The mpg readouts on my car is 5% optimist.  Checking against actual mpg over more than 30K miles.

[andy2286]

So should I assume that the first one is my overall mpg reading on that trip and the second one is an accumulated mpg from multiple trips?

[robt100]

Yep, thats Correct

[langers2k]

10 hours ago, andy2286 said:

So should I assume that the first one is my overall mpg reading on that trip and the second one is an accumulated mpg from multiple trips?

 

Almost, the first one can be multiple trips if they are close enough together. From the manual:

 

Single-trip memory (memory 1)

The single-trip memory collates the driving information from the moment the ignition is switched on until it is switched off. New data will also flow into the calculation of the current driving information if the trip is continued within 2 hours after switching off the ignition. If the trip is interrupted for more than 2 hours, the memory is automatically erased.

 

Total-trip memory (memory 2)

The total-trip memory gathers data from any number of individual journeys up to a total of 19 hours and 59 minutes driving or 1 999 kilometres driven, and on vehicles which are fitted with an information display up to a total of 99 hours and 59 minutes driving or 9 999 kilometres driven. The memory is deleted when either of these limits is reached and the calculation starts all over again. Unlike the single-trip memory, the total-trip memory is not deleted after a period of interruption of driving of 2 hours.

[andy2286]

Thank you guys, that is exactly what I wanted. How optimistic is the read out then?

[philbes]

2 hours ago, andy2286 said:

Thank you guys, that is exactly what I wanted. How optimistic is the read out then?

AS I said in my post above - "The mpg readouts on my car is 5% optimist.  Checking against actual mpg over more than 30K miles."

[langers2k]

Mine was about 13% optimistic so it varies a decent amount between cars.

 

I've adjusted the instrument cluster so it's within an mpg or two

[andy2286]

The over optimistic mpg reader, is this something which can be fixed via vcds?

[Sarge]

On my vRS the computer reading is almost spot on with the manual calculation.  

[langers2k]

41 minutes ago, andy2286 said:

The over optimistic mpg reader, is this something which can be fixed via vcds?

 

Yup, there is an adaption channel in the instrument cluster to adjust it between 85% and 115% if I remember correctly.

 

You just need to calculate how far off it is first