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Little Megger
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24 Posts
Discussion Starter · #1 ·
hi guys. had my mk3 two months now 54 plate with 86k on, filled her up with 49ltrs and have only got 380mils before light is on again. mostly town driving and 80 miles up duel carageway. i think this is bad.
any opinions.
cheers guys.
 

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MEG Corporal
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1,048 Posts
35.2 mpg average...that's a bit low IMO. When you're about town diving are you totally thrashing it?
 

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TDDI Buff
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37,060 Posts
depends how your driving it as in how many rpm's your going upto when driving.
 

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Man in a Jag
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15,051 Posts
Is this your first Diesel?

To get an accurate figure on the Fuel Economy you really need to manually calculate it. This is quite simple to do - just fill it up, run the tank down and when you come to fill up again make a note of the number of miles you have done, and the amount of fuel you have put in. Then do the following calculation:-

[color:blue]N° of miles travelled[/color] / [color:purple]N° of Litres put in[/color] = [color:red]Miles per Litre[/color]

[color:red]Miles per Litre[/color] * 4.545 = Miles Per Gallon

Anyway, from the figures you have given it does seem a little low - should be in the early 40's at least on town driving. There are a few things you can do.

Dont thrash the car - especially when the engine isnt warmed up. Use the Torque of the engine, and dont really pay that much attention to the Revs just yet, apart from making sure you arent taking it to the red-line. Changing gear between 2 and 2.5k means you are using the torque more efficiently, and dont be in any hurry to get to these (wear a lighter shoe on your right foot :) )

Try an ECU Reset. There is a 'How To' in the Workshop under Electrical, but basically what this does is removed the settings the ECU has learnt itself and re-learns according to the current setup of the car and how you are driving it. Over time, the engines loosen up so it may not have re-learnt according to its current setup.

Try some Injector Treatments. These are cheap and you just pop them into the tank when you fill up. One of two times may help. The user manual says not to use any of these treatments but it wont do any harm unless you put in more than is recommended by the make of it. I use these on my car from time to time to make sure everything is clean on the injectors.
 

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Man in a Jag
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15,051 Posts
TG - just noticed your new Signature. We'll see who needs a tuning box when I get round to getting mine on the rollers :) I'm hoping for over 140 :L
 

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TDDI Buff
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37,060 Posts
id rather keep my money for something else
 

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Man in a Jag
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15,051 Posts
'twas cheap and I could always flog it on and get my money back :L
 

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Little Megger
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27 Posts
I'm onto my 4th tank full in my 05, 115 tdci and I'm not impressed with the mpg todate. I only managed an average of 36.6 mpg on the last tank full (mostly around town) and 40.75 on the tank before (250 mile run & around town - with a bit of lead foot).

The above figures were the best i've had, as prior to this, it only appeared to be making 31-32 mpg according to the onboard computer....this actually turned out to be 35.5mph but I still thought this was naff, so took it into ford for a moan. ford reprogrammed the ecu (or so they tell me). it seemed to pull better and wasn't hesitating around 2k rpm anymore, but mpg still seems low.

For the last couple of fill ups, I've put some redex in, hoping this might help, but it still seems low.
 

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MEG Corporal
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1,133 Posts
Had my TDCi a year now, I do a twenty mile run to work on A and B roads and through one town centre.
The roads are clear in the morning and busy when I come home in the afternoon.
I'm currently getting 47mpg, it will drop when the colder weather hits and it drops in Summer when the air con is working hard but the lowest I get is about 42mpg.
On a nice steady run I can just about break 50mpg. When I have the trailer on the back I average 28-32mpg.
My wife has a Skoda Fabia 1.9 TDi and that gets around 12mpg more than the Mondeo driving the same roads.

Cheers
Lee
 

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Man in a Jag
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15,051 Posts
A lot of it is how you drive them guys - most of the waste is done by accellerating too quickly to get upto speed, and not anticipating when you will need to slow down (i.e. ragging it upto the junction the braking hard). With modern cars, when you arent touching the accelerator the car wont actually be using any fuel - put your clutch in and it will use some to tick the engine over but the wheel turning is enough to keep the engine spinning. Think of that and I guess you will start to see an increase in your economy.

Also - with the trip computer, you need to remember 2 things:-

1. They arent accurate, but are a good indication. Mine (TDDi) underestimates by about 3-5mpg when I calculate it manually, and I have heard that TDCi's can be a few MPG optimistic when you work it out manually.
2. Remeber to reset them every tankful - otherwise its just working out an average since you last reset it (which in the case of my sisters Pug 307cc is when she bought it almost 2 years ago :eyesup: )
 

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TDDI Buff
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37,060 Posts
end of the day if you want good mpg keep your revs under 2500rpm tyou can change up gears around 2000-2100rpm if your going over 2500rpm often theres your problem. if your not and your stil lgetting low mpg then its likely the car needs a good rag and possibly some injection cleaner.
 

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Little Megger
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24 Posts
Discussion Starter · #12 ·
thanks guys.
was thinking of the ecu reset. i dont drive the car hard, find my bike is enough for that. will see what happens. cheers
 

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Glen
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4,110 Posts
I have had my TDDi for 4 months now and the most i have had on a tank is 40.25 mpg and that was about 200 miles motorway and about 100-150 town/A/B roads. I regularly get between 31.8 and 38mpg mainly doing town and 10 miles B roads to work and then back again. still better than petrol though.
 

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Registered
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1,207 Posts
Last week, my TDCI returned 34mpg for a day on the track :} I usually average about 40mpg for my regular driving, but that's mainly because I don't hang about. I've seen over 50mpg where I've been good :D

If you're consistently looking at low mpg's then a few things to look at are a) plan ahead when driving round town and avoid accelerating hard/braking hard cycles b) use the full rev range as it keeps the car clag-free, won't put a strain on the DMF and also won't require you to accelerate to get going again c) make sure you remove any unnecessary junk from the car d) check tyre pressures are ok.

If the change has happened recently, it may be because the forecourts are switching over to winter diesel....

Chris
 

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MEG Corporal
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726 Posts
They don't switch to winter diesel anymore and haven't done for years. Modern diesel doesn't suffer at the temperature that we get so no need for the anti gelling agents.
Just found that out myself. :L
 

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Man in a Jag
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15,051 Posts
TdciDick said:
They don't switch to winter diesel anymore and haven't done for years. Modern diesel doesn't suffer at the temperature that we get so no need for the anti gelling agents.
Just found that out myself. :L
Are you sure? The Diesel at Shell tends to be fairly clear during the summer months, but you can see a greenish tinge once the weather starts to get cold - I assumed this is the any gelling agents they put in.
 

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MEG Corporal
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726 Posts
Well, that was the result of a conversation between a fellow VW T4 owner and a guy that works at a refinary, but if you know differently I will stand corrected.

In winter the fuel is more dense as the tank temperature will be colder, maybe that will effect the colour. Personally I never see the colour as the nozzle is shoved right in there.

Your a tap the last drop out merchant aren't you? :naughty:
 

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Registered
Joined
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23 Posts
I've had my 55 plate TDCi now since the beginning of September, first fill with mainly short town work but a couple of 50 mile round trips gave 44mpg second trip out gave 39.5 mpg over 400 miles with half towing a large caravan. third fill was 45mpg again mainly very short town journeys with two or three 50 mile round trips. All these figures are actual not computer. I know that if I make longish trips that I get mid 50's it's the only way to make sense of the figures from the computer.
 

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Man in a Jag
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15,051 Posts
TdciDick said:
Your a tap the last drop out merchant aren't you? :naughty:
Nah - I just look at the nozzle when I take it out - there is always the odd drip that comes off. :)

Im just going off the past few years of Diesel Ownership - noticed that the colour does change when it gets colder (not gradual - one day it could be clear when filling, the next it could be like washer fluid colour). Just presumed it was an additive they put in or it might just be Shell Diesel Extra as I always fill up with that stuff.

As far as MPG goes - Ive monitored MPG in my Diesels, and the other halfs Petrol over the past few years and it does reduce in the colder weather, although thats probably less due to any additives and more due to the actual temperature itself as it goes down by upto 5mpg in the missus little Petrol.
 

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MEG Corporal
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1,133 Posts
ScoobyChris said:
Last week, my TDCI returned 34mpg for a day on the track :} Chris
That's a bit better than the Scoob, I took it to Oulton Park from Mansfield.
Averaged 8mpg on track and 12mpg for the day.
Put £200 of fuel in it on the one day and petrol was only around 75p a litre then. :)

Cheers
Lee
 
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