50mpg from 1.4TDI90 on long trip - normal?

Edwrai

Member
Although Audi quoted similar mpg figures for both the TDI 75 and 90 variants in the real world and having owned numerous 75's and a couple of 90's the difference in mpg is huge BUT in favour of the 75 like 99.9% of people who have owned them will agree and by around 8-10 mpg from my experience.

To average 78mpg in either of my 90's i would have needed to be going downhill with the clutch depressed

Mpg in the 50's is pretty much the norm for a 90 and 60's for a 75.

These figures are obviously dependant on everything being in tip top order and working as they should. No binding rear brakes, under pressure tyres and faulty temp sender/thermostats

Here is 20k of travelling I tracked before getting bored of filling in the app


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Edwrai

Member
Although Audi quoted similar mpg figures for both the TDI 75 and 90 variants in the real world and having owned numerous 75's and a couple of 90's the difference in mpg is huge BUT in favour of the 75 like 99.9% of people who have owned them will agree and by around 8-10 mpg from my experience.

To average 78mpg in either of my 90's i would have needed to be going downhill with the clutch depressed

Mpg in the 50's is pretty much the norm for a 90 and 60's for a 75.

These figures are obviously dependant on everything being in tip top order and working as they should. No binding rear brakes, under pressure tyres and faulty temp sender/thermostats

Honestly I can’t get my 90 below 50-55 mpg even if I drove it flat out everywhere.


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PaulHa

Member
The spritmonitor.de search tool suggests an average of 58.25 mpg for the 75 Tdi (243 vehicles) and 57.17 mpg from the 90 TDi (137 vehicles).

I have averaged 66.2 mpg in my TDi 90 over the last 10 years with light footed driving as measured at the tank on refills, although having upgraded to Bridgestone Turanza T005 tyres ('B' rated rolling resistance) 2 years ago the average has been 70.9 mpg - so tyres can make quite a difference- but limiting your maximum highway speed probably has as big an impact.
 

dj_efk

A2OC Donor
Hi all,

Just to add some nice colour to this thread - I stumbled across an ancient post by @Jeetesh from 2007 (Impressive stamina with the A2 and this forum considering he's still with us!) so @Jeetesh I hope you don't mind me sharing your wisdom here on what you've found works well for improving our cars' fuel consumption:

a few hints and tips

- Add a couple of psi to each tyre, it decreases rolling resistance, Michelin Pilot premacy tend to be good for economy, better than bridgestones or pirellis
- remove all unnecessary junk we all carry in our cars
- ensure oil is topped up
- try a fuel additive, this added 3-4 mpg to my car
- remove the back seats, this would add circa 6mpg although not good for security as it leaves items exposed. If you have surprise passengers its not good so this ones a bit extreme. It does however improve overall performance for nothing, fantastic for outrunning rep mobiles on motoways.
- Ease off towards red lights and avoid stopping where possible
- Dont sit with the engine running unnecessarily
- Turn the climate to economy mode
- Drive where possible at constant speeds without heavy acceleration or deceleration
- drive behind some one else in strong head winds on motorways (not tailgating), you'd be surprised at the difference this makes
- Turn off unnecessary electrical items, heated seats etc. This you probably wont notice any difference.

I used to do most of these things and I would average anywhere between 60 and 70mpg regularly and this was diased towards motorway to urban 60%/40% respectively.

Previous comments on that area of the country make a huge difference, when I was living in Essex I would get circa 10mpg more than where I now live in Halifax.
 

Sidewinder

Member
I’d be interested if anyone knows how their diesel timing is? Cam belts stretch over their lives and can knock out the timing a little, and was it even checked when the belt was changed? I’m no expert but have been told that it’s ok to run with a slightly negative torsion value on VCDS to improve MPG (around -1.7 to -2.5) without losing much performance, and that you don’t want it to be slightly positive.

I’ve just done cambelts on both mine, I set the 75 to 0.0 and the 90 was -1.7 after change so I left it at that? I may change the 75 to -1.7 but would welcome anyone’s advice/ experience/ knowledge on the matter.

Andy
 

dj_efk

A2OC Donor
An excellent question - I was going to check Audrey’s torsion values when I next scan the car. There’s not much clarity on this out there so trying to research just digs up conflicting info.

I’d be interested to know if you notice a difference after knocking the timing back on the 75, although my primary interest is with the 90 engine
 

Sidewinder

Member
An excellent question - I was going to check Audrey’s torsion values when I next scan the car. There’s not much clarity on this out there so trying to research just digs up conflicting info.

I’d be interested to know if you notice a difference after knocking the timing back on the 75, although my primary interest is with the 90 engine

I’ve noticed no lack of performance with the 90 on -1.7 (it actually toggles between -1.7 and -2.2) but I didn’t know what it was before belt change so I can’t say what it was like at 0.0, I’ll have to do a comparison performance wise on the 75 when I change it from 0.0 to -1.7ish, the problem is I don’t do many miles in either car to run proper tests.

I’ve recently also run liqui moly purge through both engines, a litre in a litre vodka bottle tied ro the air piping, run through until it was half full, the 1/2 litre left in the bottle on the 90 was a LOT clearer than the 75, The 90 has been running with a double shot of millers diesel ecomax per tank for past 6 months.

Andy
 

VAG fool

Member
Q for the OP: how fast do you drive on the motorway?
So you drive in "clean" air or catch yourself being buffeted in turbulent flow?
 

dj_efk

A2OC Donor
You LOST weight in lockdown? How?!

@Sidewinder - I too have run Millers through the car whenever I’ve had it (my brother in law is borrowing it but I use it regularly and put a full tank in it when I hand it back, along with a double shot) - plus I ran 5L of diesel purge through the system via a nearly-empty tank recently as you may know if you’ve read my blog thread. Consumption has improved a fair bit, although some of that would have been due to warmer weather I’m sure - but not all of it.

The next experiment is to see whether I can achieve any further consumption improvement by adding 250ml of Jaso FC spec semi-synthetic two stroke oil to the tank - @timmus do you still do this?

Getting around 62-64mpg on long journeys cruising at 65-70mph and allowing the speed to drift up and down according to the terrain now.
 
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DuncanA2

Member
I have explored this as well. I found out that our 90bhp tdi are susceptable as well to fine tuning the torsion value (TV) of the timingbelt. (MMB 04,04). From what I understand the ideal TV is 0,0 or as close possible, but there are examples of different TV with good/ better results.
I've tried several TV on mine. My general impression is that negative values (-) correlates to advanced TV setting and results in to less bottom end and hapoy revving engine. Positive values (+) correlates to retarded TV setting and results is more / earlier torque downlow and less happy to revving the engine.
Advanced TV increases the consumption and retarded TV decreases consumption.

So if you have a TV of -3⁰ you have a higher fuel consumption than at +3⁰ TV.
In my case this meant 1:18 or 1: 23. I.e. 50MPG or 67MPG.
 

dj_efk

A2OC Donor
I have explored this as well. I found out that our 90bhp tdi are susceptable as well to fine tuning the torsion value (TV) of the timingbelt. (MMB 04,04). From what I understand the ideal TV is 0,0 or as close possible, but there are examples of different TV with good/ better results.
I've tried several TV on mine. My general impression is that negative values (-) correlates to advanced TV setting and results in to less bottom end and hapoy revving engine. Positive values (+) correlates to retarded TV setting and results is more / earlier torque downlow and less happy to revving the engine.
Advanced TV increases the consumption and retarded TV decreases consumption.

So if you have a TV of -3⁰ you have a higher fuel consumption than at +3⁰ TV.
In my case this meant 1:18 or 1: 23. I.e. 50MPG or 67MPG.
Wow, that’s a massive difference!

So for clarity, what torsion value should us ATL owners be aiming for?
 

DuncanA2

Member
A
Wow, that’s a massive difference!

So for clarity, what torsion value should us ATL owners be aiming for?
Hi,

That depends on what your preference is and what you are looking for. This is only my own experience with my specific ATL.
So it could be slightly different in your case. Is it economy? I had best results with retarded TV of approx. +2.2⁰ - +5.5⁰. On a flat highway cruising steady 60mph gave 76mpg. But downside , Good torque downlow but sluggish above 3000rpm.
Is it performance? I had best results with adavanced TV of approx. -2⁰ to -3,5⁰ . Slightly less torque downlow, but easy revving beyond 3000rpm. So good power up de revs. Downside was that the torque was bit peaky, or nervous for my taste and peak torque shifted up the range 200-300rpm. The consumption was siginificant higher.

I finally ended up range at TV of 0,0⁰ with a small retarding to +0,6⁰ . This gave good drivability (torque) and decent consumption at speed. This is where I am, most of the time.

Interesting to mention is that idle compensation (MMB 13) gave the smallest differences among the cylinders. My idle consumption is 0.6L/H. Overall consumption is 67mpg.
This is with the original GRJ gearbox, so a bit higher ratio than the MPY 6-speed.

As you know through time the timingbelt stretches a bit, so it would not harm to check your TV halfway the change interval of the belt. Also under load the timing retards approx. 0,5⁰ TV. So under load I have 1,0⁰ retardation of the timing for good torque.

If you like to persue this experiment, I'd suggest you do so. I'd recommend it highly.
 
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depronman

Member
I have explored this as well. I found out that our 90bhp tdi are susceptable as well to fine tuning the torsion value (TV) of the timingbelt. (MMB 04,04). From what I understand the ideal TV is 0,0 or as close possible, but there are examples of different TV with good/ better results.
I've tried several TV on mine. My general impression is that negative values (-) correlates to advanced TV setting and results in to less bottom end and hapoy revving engine. Positive values (+) correlates to retarded TV setting and results is more / earlier torque downlow and less happy to revving the engine.
Advanced TV increases the consumption and retarded TV decreases consumption.

So if you have a TV of -3⁰ you have a higher fuel consumption than at +3⁰ TV.
In my case this meant 1:18 or 1: 23. I.e. 50MPG or 67MPG.

Hi
Can you confirm that the last sentence is the correct way around please
It may be my haggled brain (it’s been a long day) but if I’m reading the post correct the first part seems to contradict the last part
If I’m reading it wrong then fair enough but it’s bot clear to me

Cheers. Paul


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DuncanA2

Member
Hi Paul,

There is no contradiction in the last sentence. But to be clear on advancing and retarding, the indication - for advancing and + for retarding is rather counter intuitive to me. Maybe it is better to describe advancing TV is adaptation clockwise and retarding TV is adaptation counter clockwise of the camshaft in relation to the cranckshaft.
 
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dj_efk

A2OC Donor
Hi
Can you confirm that the last sentence is the correct way around please
It may be my haggled brain (it’s been a long day) but if I’m reading the post correct the first part seems to contradict the last part
If I’m reading it wrong then fair enough but it’s bot clear to me

Cheers. Paul


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It took me 3 times to understand it myself

@DuncanA2 i don’t really use the revs above 3000rpm, in fact especially with the sixth speed fitted I rarely go above 2500rpm, so as my car has so much power from its remap I’d be willing to gain some FE and have a haircut on my powerband range.

I rather get the feeling that we could be on to something here that might explain why some 90 / ATL owners get such poor consumption when compared to others and to 75 owners
 
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dj_efk

A2OC Donor
Religiously. :)
Tom do you use some kind of measure and decant the oil into that and carry it around with you? The oiler bottles I use for the Millers only hold 130ml so looking for another solution for my experiment. I recall @DJ 190 said he used old squeezy honey bottles, maybe raiding our plastic recycling bin in the kitchen could be the way to go 😂
 
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