50mpg from 1.4TDI90 on long trip - normal?

Perhaps I'm being unreasonable, but I see other threads here with people mentioning 60-70 mpg from their TDIs. I've never seen more than low 50s.

I've got an 04 TDI 90 Sport now running on 15" pepperpots - partly for efficiency and partly for comfort. It's just had a full service - fuel filter, the lot. I use Tesco diesel fuel. I drive with the Climate Control on auto. I don't have any fault codes logged. Everything seems to work and it drives normally. I have rear disks rather than drums so don't think anything is binding there, nothing is getting hot. The only thing I've ever noticed with the car has been what I can only describe as a "chirping" noise under full-load in 2nd or 3rd gear. It's always done this, it may well be completely normal - i've always assumed it was some sort of boost noise from the turbo, or general induction noise. It lasts for a couple of seconds and then goes as the revs rise or the load decreases.

I've had several trips to the airport recently, which is generally a 150 or 200 mile round trip depending upon where I'm going. This is pretty much all motorway and even the link road to the motorway is all dual carriageway for me so there must be perhaps 5 miles at best of stop/start driving. The rest is cruising at an indicated 65mph which the satnav says is actually 60mph.

I've calculated my fuel consumption by noting my miles against every tank fillup and doing the maths. On the last long trip I calculated 51.5 mpg. I fill up when the fuel warning goes off and only fill the tank to the click on the pump, but I can't see that matters too much if I'm calculating the fuel use to refill the tank anyway. I terms of mileage, I'm getting around 375 miles from a tank until the warning sounds. This is all best-case - if I potter around town or whatever I'm getting less, though it's never so far dropped below 325 miles so it isn't making a huge amount of difference.

Am I being unreasonable expecting 60 or even 70mpg? I would think on a long motorway trip at 65mph I would get at least 60 mpg, but I'm not getting anywhere near that even being very careful.

It isn't the end of the world by any means, just wondered if it meant that something wasn't quite right somewhere that I needed to worry about. And lets face it, one of the reasons I drive around looking slightly ridiculous in this car (according to my wife) is because it's cheap to run..

I have full VCDS/VAG-COM so I can gather data if necessary, just need something to compare it to.

Thanks,
Steve
 

dan_b

Member
Hi Steve
When I first got my TDi I was also getting low-50s. A combination of a few mods, a few bits of maintenance, plus an evolving driving style, has seen my average MPG go up fairly significantly.

Low-50s is actually pretty reasonable if you think about it, there aren't that many cars that can churn that sort of average MPG out without too much effort. However, if you want to chase higher MPGs, you could consider the following:

1. change the thermostat and temp sender - even if they're not showing as particularly off, there could be an underlying pathology here - the A2 is rather renowned for the stats and temp senders going technical, and they're cruicial for maintaning optimum MPG.

2. consider fitting the 1.2TDi aero mods - wheel arch lip spoilers, sub-frame spoiler and exhaust tunnel cover. It improves the aero a little and might give you a bit of an MPG boost.

3. increase your tyre pressures - I used to run my 15s at 42PSI. MikeMars runs his 15s at 46PSI. Higher tyre pressures reduces rolling resistance and improves fuel economy. Try it - it's free!

4. Switch off air-con until engine is up to 90.

5. Switch off the engine at traffic lights/jams (if you think you'll be stopped for more than 20secs).

6. Splurge big bucks on a transmission mod to lengthen gearing - either a longer 5th gear (which is what I've done) or adding in an extra 6th gear (which is what MikeMars and Timmus have both done).

7. Be really obsessive about eeking out more miles from modifying your driving style - eg. experiment with pulse&glide, working out where you can use overrun fuel-cut off mode, lighter acceleration, change up earlier etc...
 

Adrian888

Member
I would echo all the above, my mapped 75 with most of the above mods now gives 60+mpg up from an early ownership of 50+ even tho' it has gained 100k miles in the meantime.
 

MikeMarsUK

Member
... I've got an 04 TDI 90 Sport now running on 15" pepperpots - partly for efficiency and partly for comfort.

What pressure are you running at? If it gets below 30PSI (when measured cold) your MPG will drop significantly. I run at higher pressure as Dan has mentioned, but the vital thing is that you never drop below the recommended. If you have a sport, that probably means that you started with the 17" wheels - this would have cost you a few mpg if you had not already changed them to 15s.


... I drive with the Climate Control on auto. ...

I normally have the compressor turned off (but remember to turn it on at least once per month to keep the seals lubricated). However the mpg impact of climate control is worse on short distance / low speed driving rather than long distance driving.

... I've had several trips to the airport recently, which is generally a 150 or 200 mile round trip depending upon where I'm going. This is pretty much all motorway and even the link road to the motorway is all dual carriageway for me so there must be perhaps 5 miles at best of stop/start driving. The rest is cruising at an indicated 65mph which the satnav says is actually 60mph. ...

I think you should be seeing 70mpg+ for these trips, but there are many things which can disrupt your mpg. Keep in mind that if you do 150 miles at 70mpg, and 150 miles at 40mpg, your combined mpg is 51 not 65.

Did you have a roof rack / roof box / trailer / bikes mounted for the airport trip? Any of these things would hurt the aerodynamics (which mainly affects A-road & motorway driving).

What was the weather like at the time? Your mpg will be better in the summer than the winter (as long as air-con is off, anyway).

... I fill up when the fuel warning goes off and only fill the tank to the click on the pump, but I can't see that matters too much if I'm calculating the fuel use to refill the tank anyway. ...
You are right, it will not affect your MPG (but will affect your range per tank).

... if I potter around town or whatever I'm getting less, though it's never so far dropped below 325 miles so it isn't making a huge amount of difference. ...

Normally short distance / stop/start driving is much worse on mpg than long distance driving (particularly in winter, or if the climate control is active). So your town driving mpg is reasonable, but I think it is suspiciously low on long distance tanks. How much of your tank was long distance versus town driving? i.e., if only 50% of the tank was long distance, then you would still expect your overall tank to mainly reflect the town driving.




If you have a sport, then you should have the DIS option which can give you an indication of the MPG for individual trips & the full tank. While calculating manually is always more accurate, it is helpful to get the feedback from individual journeys.
 
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What pressure are you running at?
from memory, around 35psi. I'm going to up that as per the advice above
If you have a sport, that probably means that you started with the 17" wheels
Correct - changed to 15" a couple of months back and has probably increased mpg by a small amount - +2 or +3 average maybe? I think I was maybe 47ish now 50ish.
Did you have a roof rack / roof box / trailer / bikes mounted for the airport trip?
No.
What was the weather like at the time?
A mixture. One trip was a couple of days ago, good weather.

How much of your tank was long distance versus town driving?
The last couple of tanks on long trips were probably 85%-90% motorway.

If you have a sport, then you should have the DIS option which can give you an indication of the MPG for individual trips & the full tank.
Yes, I have DIS and it's reasonably accurate against my calculated figures. I think it says 47mpg at the moment, but it hasn't been reset for ages.
 
I have recorded every drop of diesel I have put in my 1.4 Tdi 75 since I bought it new in Sept 2002. Recently calculated overall consumption for every kind of use except very short journeys (don't do those) at 66.04 mpg. Pretty pleased with that but 90 model would obviously use a bit more.
 
It does seem a little bit low to me seeing as I can get 46+ on a long motorway journey with the petrol if I'm very careful...this is with sport alloys as well...perhaps turning off the AC
completely would help a lot; my car is one of the few without it so its not a concern!

Cheers
 

John L

Member
Turning the aircon off in very cold temps is a big no no. The windows steam up and you can see nothing.
People breathing inside in -15c is deadly without the aircon on.
 

MikeMarsUK

Member
... Yes, I have DIS and it's reasonably accurate against my calculated figures. I think it says 47mpg at the moment, but it hasn't been reset for ages.

If it is consistent with your tank figures, it is worthwhile keeping an eye on it (reset for each tank etc). The feedback is useful and helps develop your driving style.

Which figures does the A2 DIS show? My old Passat had instantaneous mpg, journey mpg, and tank mpg. The journey mpg in particular was very useful.

Regarding climate control, I tend to turn on the heater at 10c or below, the webasto at 0c or below, and turn on the compressor at 25c or higher. But these all add quite a bit to your fuel consumption.
 
Are we agreed that there is actually an issue with the fuel economy of the car? I can see things like tyre pressures, aero mods making a small amount of difference, but not the 10 or even 20mpg I seem to be missing on long journeys compared to some other cars here. And if it was just a heavy right foot on my part, wouldn't my town driving be down to horrible figures (e.g. 275 miles/tank) too?

Perhaps I need to get the Temp Sender and Thermostat swapped out just to see what happens.
What other things are there that would affect fuel consumption without giving fault codes or obvious running problems? MAF sensors and the like maybe?

Or am I making too much of it?
 

dan_b

Member
I'd say that it might be a little on the low side from what one might expect if you were doing mostly motorway cruising at around the 60mph mark.
 
Mine has been a constant 60mpg; 75hp, sometimes climate, sometimes not... windows open, ours has done this from 0-200,000 miles, it's stock and has no mods.

I think yours is a little on the low side, but not enough to worry about.

I'm amazed if a chipped TDi 90 could do 77mpg, perhaps I should get mine chipped, for the next 200k!


bba
 

MikeMarsUK

Member
Mine shows instantaneous MPG and total MPG since last reset. I guess I should reset it on every tank fill.

It might also be worth resetting it just before a long motorway trip to see what mpg a 100% long distance journey gives you.

Your town driving sounds normal in terms of mpg, but your long distance driving seems low.

... What other things are there that would affect fuel consumption without giving fault codes or obvious running problems? MAF sensors and the like maybe? ...

Virtually anything. There are few problems which won't result in a dropped mpg. Because there are so many different things it might be, it makes it very difficult to diagnose if the only symptom is the mpg.
 

RAB

Technical Specialist 1.2 TDI
As your car is a 90 it will have a VNT turbo. Check that the VNT mechanism can move freely by pressing down the lever on the actuator on back of the turbo. If not it may need dismantling to clean it. It can make a big difference to fuel consumption (10-15%) without triggering a fault code.

RAB
 

timmus

A2OC Donor
I recently drove my friend's car (this one: www.a2oc.net/forum/showthread.php?22191) from Lancaster to Vince's place in Southam. It's a completely standard TDI75 and I got exactly 70mpg by holding as close to 60mph as my foot would allow. As Terry said above, he managed 77mpg from his remapped TDI90 when he came to visit me in Lancaster from his home near Bristol.

With this in mind, I'd suggest there is something amiss with your car. Your urban economy is roughly what I'd expect, but those long journeys should be returning a higher figure.
As others have suggested, I'd try changing the dual temp sender. If the ECU-side sensor is on the blink but the cluster-side sensor is fine, you'd never know there was a problem.

RAB's suggestion is also good - as ever!

Whilst it wont affect your cruising economy, am I right to assume that you're familiar with how to drive a TDI for fuel economy? As others have said, adapting your driving style will have an enormous impact upon your efficiency. The mother of a friend of mine recently bought an A2 TDI having been so impressed by the versatility of mine. However, she drives it like a petrol - from cold! She's expressed disappointment about the car's economy, but continues to change gear when the engine sounds strained rather than on the basis of the torque curve.

Cheers,

Tom
 

RAB

Technical Specialist 1.2 TDI
Turning the aircon off in very cold temps is a big no no. The windows steam up and you can see nothing.
People breathing inside in -15c is deadly without the aircon on.
John,

I believe that the cooling/dehumidifier component, i.e. the compressor, of the A/C shuts down at an ambient temperature of 5 deg C or below anyway, otherwise it will freeze up completely, so below that temperature it doesn't make much difference whether you choose the ECON setting or not - if that's what you mean! If you look at the spec of a non-auto A/C, they only cool down to 5 deg C.

RAB
 

terrywindy1

Member
bye bye alfa be amazed then
I'm amazed if a chipped TDi 90 could do 77mpg, perhaps I should get mine chipped, for the next 200k!
 

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