50mpg from 1.4TDI90 on long trip - normal?

Well, it was close, but 500 miles from 37 litres is not too bad. Bit disappointed in the 56.8mpg as I had 60mpg for most of this tankful, but then 512 miles from 8.18 gallons = 62.59 mpg!? What could make my DIS that far out, or is this normal?

Mostly 55/65 mph on motorways and A roads. I did a fair bit of 70+ for the last 100 miles and blasting the cc too so I reckon 550 miles from a tank is fairly easy to achieve. I wont be running the tank so low again though so will add +5 mpg to my DIS reading in future. Also going to try some Miller’s as recommended from earlier in the thread and finally fix the fuel temp sensor wiring!
 

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When WOM repaired the wiring on my Crystal TDI's fuel temp sensor it made the engine run a lot sweeter and quite probably more economical. A steady 60mph on the cruise now gets me over 70mpg on a motorway run of a couple of hundred miles.
 
froggy said:
Well, it was close, but 500 miles from 37 litres is not too bad. Bit disappointed in the 56.8mpg as I had 60mpg for most of this tankful, but then 512 miles from 8.18 gallons = 62.59 mpg!? What could make my DIS that far out, or is this normal?

Mostly 55/65 mph on motorways and A roads. I did a fair bit of 70+ for the last 100 miles and blasting the cc too so I reckon 550 miles from a tank is fairly easy to achieve. I wont be running the tank so low again though so will add +5 mpg to my DIS reading in future. Also going to try some Miller’s as recommended from earlier in the thread and finally fix the fuel temp sensor wiring!
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By my reconning 5-10% under read from the DIS seems to be pretty standard vs the manual calculations I do. We’ll done on breaking the 500 though!!! ?
 
froggy said:
Well, it was close, but 500 miles from 37 litres is not too bad. Bit disappointed in the 56.8mpg as I had 60mpg for most of this tankful, but then 512 miles from 8.18 gallons = 62.59 mpg!? What could make my DIS that far out, or is this normal?

Mostly 55/65 mph on motorways and A roads. I did a fair bit of 70+ for the last 100 miles and blasting the cc too so I reckon 550 miles from a tank is fairly easy to achieve. I wont be running the tank so low again though so will add +5 mpg to my DIS reading in future. Also going to try some Miller’s as recommended from earlier in the thread and finally fix the fuel temp sensor wiring!
Click to expand...
As per my blog thread - I've noticed that on both TDI90's I've owned, DIS is around 15% pessimistic on the average fuel consumption calculation (and therefore, one assumes, the instant readout too).

As Erling confirms above, this seems to be pretty common and not just my experience. Interestingly I do not see TDI75 owners reporting this however!

My best tankful was also 63 mpg and that was with a six speed, so I would say yours is now behaving itself @froggy. You could try a diesel purge and running Millers as per the instructions on the bottle to see what happens (or else just running a bottle of Millers at double strength to give some of the same effect if you're not too handy / confident of doing a purge).
 
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dj_efk said:
As per my blog thread - I've noticed that on both TDI90's I've owned, DIS is around 12-15% pessimistic on the average fuel consumption calculation (and therefore, one assumes, the instant readout too).

As Erling confirms above, this seems to be pretty common and not just my experience. Interestingly I do not see TDI75 owners reporting this however!

My best tankful was also 63 mpg and that was with a six speed, so I would say yours is now behaving itself @froggy. You could try a diesel purge and running Millers as per the instructions on the bottle to see what happens (or else just running a bottle of Millers at double strength to give some of the same effect if you're not too handy / confident of doing a purge).
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It’s exactly the same on the 75bhp David. Also the same on the 1.2!

Second the advice on the Millers. I tend to bulk buy from Opie Oils when they have discounts on.
 
dj_efk said:
As per my blog thread - I've noticed that on both TDI90's I've owned, DIS is around 12-15% pessimistic on the average fuel consumption calculation (and therefore, one assumes, the instant readout too).

As Erling confirms above, this seems to be pretty common and not just my experience. Interestingly I do not see TDI75 owners reporting this however!

My best tankful was also 63 mpg and that was with a six speed, so I would say yours is now behaving itself @froggy. You could try a diesel purge and running Millers as per the instructions on the bottle to see what happens (or else just running a bottle of Millers at double strength to give some of the same effect if you're not too handy / confident of doing a purge).
Click to expand...

For those of us with colour DIS there is actually a way to make up for this in the setting so that you get a more accurate live reading.
 
I think there is a way to calibrate the dis consumption on the none colour dis as well
Sure I read something on vcds about doing this calibration


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Hi all, I've just filled up Audrey after 384 miles and fitted 29.13l into the tank by brimming whilst venting as I always do. I calculate this to be almost exactly 60mpg, most of this tank was 70mph cruising (although it included a brief detour to @Jason_e 's gaff with his new bonnet over A roads in Wiltshire and Oxfordshire). 150 miles of this was with a fully loaded, heavy car on the return journey from Maidenhead this week (I now have some more A2 parts to sell as well as more general bits left over from my classic car tinkering days!).

My DIS said 53mpg, hence I can confirm my car is circa 15% pessimistic on fuel consumption figures and hence I will have a go at adjusting the correction factor via Colour DIS as Thomas / @gangitano85 indicates and will then report back. Anything CDIS can do you should also be able to do with VCDS on a car that is not so equipped.

As a side-note, I still had half a tank left according to the gauge (I didn't check the exact fuel amount remaining though, the ability to do so is another feature of CDIS and appears to be dead accurate save it only reads up to a maximum of 42l) - and CDIS said I had 220 miles of range left.

Just to re-confirm, as above I run supermarket fuel with the Millers Diesel Additive at the recommended dose (although I tend to err on the side of over, if anything). I'm not sure how relevant that is because as I've previously noted in the thread on this subject, I've not noticed a boost in MPG since using it in my Touran, however I am confident it keeps my fuel system clean such that I'll never need to do another diesel purge to restore lost efficiency - and is cheaper to run the car this way than using top branded fuel (currently working out at 8p a litre cheaper at Tesco even with the cost of the additive factored in, meaning a full tank of 45l (running it down to zero miles range) saves me £3.60.
 
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How do you work the little button thingy in the tank neck? Is it a lever or push in etc? I saw it today but couldnt do much with the little nipple :cool:
 
Once the pump "clicks off" as "full", use the lip of the nozzle end to push the button in the neck and simultaneously fill gently until fuel is about to spill out - you'll get another 3/4 litres in there at least. Doing this enables you to be sure you've mostly eliminated the variance between different pumps' sensitivities as to when they click off - hence ensures more accurate MPG calculations.

It's only a tiny little thing and it takes practice to stop the end of the nozzle slipping off it mind!
 
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I've measured the actual MPG of my car after 3 fill ups. I tend to not go below a 1/4 of a tank a lot, so not a FULL tank put in, however, they are as follows:

  • 58.0Mpg - 24.5L- Apr 6th - This was when the car was completely standard. And involoved one long motorway slog of a day!
  • 57.4Mpg - 22.18L - Apr 20th - At least half of this tank was after JDD Box and a remap, but I cant fully remember.
  • 64.7Mpg - 23.170L - May 12th - This is after I've sorted pretty much ALL the issues, serviced the car properly and added the millers diesel additive. Its also had the undertray fitted and the car lowered.

My driving is mostly A and B roads with some duel carriageway. Lots of stopping and starting too! And, shamefully, a lot of short journeys too! I'm really not trying to hypermile it but satisfying all the same. I usually go to the first or 2nd click on the pump. Thats all.
 
I very often hear that the DIS is inacurate. On our FSI Sport, (on 17"s), the DIS average is 46.5 mpg, supported almost exactly by the brim to brim spreadsheet I've run since we got it 3 years ago.
Mac.
 
PlasticMac said:
I very often hear that the DIS is inacurate. On our FSI Sport, (on 17"s), the DIS average is 46.5 mpg, supported almost exactly by the brim to brim spreadsheet I've run since we got it 3 years ago.
Mac.
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Most of the time my averages for the tankful as shown on DIS and ColourDIS when I fill up, are within 0.5% of my calculated figures from brim-to-brim (vented) fills. DIS can be a little optimistic in the winter on my Crystal one, I think the Webasto drinks more than DIS gives it credit for.
 
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