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Author Topic: Poor MPG theory doesnt match actual  (Read 4688 times)

Offline jakex181

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Poor MPG theory doesnt match actual
« on: October 28, 2013, 09:37:05 am »
Hi Guys,

I dont know if i have an issue here but...

My dash reads an overall average of 30mpg but when i use an online calculator or calculate it on paper it should actually read far less.

If i put £20 of fuel in at 1.29/litre (standard unleaded) i personally get 80 miles, but if im actually achieving 30mpg i should be seeing 100ish miles.

Could the lost 20 miles be because of starting/idling and similar things or could i have a deeper issue?

Offline Marc-5-GTI

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Re: Poor MPG theory doesnt match actual
« Reply #1 on: October 28, 2013, 10:13:28 am »
The electronic read out is never going to be spot on..

If you're really troubled by it though, keep an eye on it.
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Offline GrayMK5GTI

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Re: Poor MPG theory doesnt match actual
« Reply #2 on: October 28, 2013, 10:15:37 am »
I think the accuracy can be adjusted with VCDS (Vag Com) if you can work out how far out it is manually.
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Offline jakex181

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Re: Poor MPG theory doesnt match actual
« Reply #3 on: October 28, 2013, 10:39:17 am »
Ok cheers guys im just going to keep an eye on it for now and maybe start logging my fill ups

Offline Leigh200sx

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Re: Poor MPG theory doesnt match actual
« Reply #4 on: October 28, 2013, 10:49:10 am »
Wish mine did 30mpg... I'm sure there is something wrong with It, I've had a Leon Cupra r running 270 Bhp and that was really really good... My gti is doing around 24mpg on the clock and over a long run maybe 30mpg

Offline SurreyED30

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Re: Poor MPG theory doesnt match actual
« Reply #5 on: October 28, 2013, 10:53:53 am »
^ +1 about the golf
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Offline alexmccabe

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Re: Poor MPG theory doesnt match actual
« Reply #6 on: October 28, 2013, 11:36:37 am »
I get nearly 38MPG+ out of mine on my drives to and from work. I hit up cruise control at 65mph and just relax. Saves me a lot of money. I am still convinced it is not running right as well, so tomorrow it is going to a garage for diagnostics. :) Maybe you should just get a diagnostic scan just to be sure.


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Offline xjay1337

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Re: Poor MPG theory doesnt match actual
« Reply #7 on: October 28, 2013, 11:59:08 am »
I get around 36-38 on longer more chilled out drives.
Around 450 to a tank seems quite healthy to me.

Offline Simon_2.0t

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Re: Poor MPG theory doesnt match actual
« Reply #8 on: October 28, 2013, 12:00:47 pm »
I get nearly 38MPG+ out of mine on my drives to and from work. I hit up cruise control at 65mph and just relax. Saves me a lot of money. I am still convinced it is not running right as well, so tomorrow it is going to a garage for diagnostics. :) Maybe you should just get a diagnostic scan just to be sure.

I was of the understanding using Cruise control not a great way to achieve good MPG as is constantly adjusting the fuel to maintain speed?

38 great figure tho  :happy2:

Offline GrayMK5GTI

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Re: Poor MPG theory doesnt match actual
« Reply #9 on: October 28, 2013, 12:04:42 pm »
I get nearly 38MPG+ out of mine on my drives to and from work. I hit up cruise control at 65mph and just relax. Saves me a lot of money. I am still convinced it is not running right as well, so tomorrow it is going to a garage for diagnostics. :) Maybe you should just get a diagnostic scan just to be sure.

I was of the understanding using Cruise control not a great way to achieve good MPG as is constantly adjusting the fuel to maintain speed?

38 great figure tho  :happy2:

I get roughly the same with or without using Cruise Control  :happy2: Makes a journey so much easier
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Offline alexmccabe

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Re: Poor MPG theory doesnt match actual
« Reply #10 on: October 28, 2013, 01:50:33 pm »
I get nearly 38MPG+ out of mine on my drives to and from work. I hit up cruise control at 65mph and just relax. Saves me a lot of money. I am still convinced it is not running right as well, so tomorrow it is going to a garage for diagnostics. :) Maybe you should just get a diagnostic scan just to be sure.

I was of the understanding using Cruise control not a great way to achieve good MPG as is constantly adjusting the fuel to maintain speed?

38 great figure tho  :happy2:

I actually get less MPG out of it if I don't use the cruise control. It is a lot harder to maintain a constant speed using only your foot. I'd say it's well worth forking out for it if you haven't got it. Might save you some money.


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Offline jakex181

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Re: Poor MPG theory doesnt match actual
« Reply #11 on: October 28, 2013, 02:38:11 pm »
How can i go about getting diagnostics done? do i just take it to any garage or must it be VW?

Offline dodds-gttdi

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Re: Poor MPG theory doesnt match actual
« Reply #12 on: October 28, 2013, 03:26:29 pm »
Ok cheers guys im just going to keep an eye on it for now and maybe start logging my fill ups

A really useful (and free!) app I use is called Roadtrip. Handy wee thing to log all your fill-ups and calculates your MPG, etc, etc.  :happy2:

Offline alexmccabe

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Re: Poor MPG theory doesnt match actual
« Reply #13 on: October 28, 2013, 04:48:27 pm »
How can i go about getting diagnostics done? do i just take it to any garage or must it be VW?

Many garages will charge you a ridiculous amount for it. Best bet is to find someone that can do it for you. There is bound to be somebody in your location that has VAGCOM.


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Offline Baz300

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Re: Poor MPG theory doesnt match actual
« Reply #14 on: October 28, 2013, 05:05:52 pm »
Wish mine did 30mpg... I'm sure there is something wrong with It, I've had a Leon Cupra r running 270 Bhp and that was really really good... My gti is doing around 24mpg on the clock and over a long run maybe 30mpg

Have you checked the diverter valve?

My car was getting crap MPG before I replaced the torn one