125tdi woeful fuel economy, help!

[brad]

I'm pretty sure that considering the OP's problem, its definitely NOT his technique at measuring fuel economy that is the issue here. Everyone please stop cluttering up the thread with advice about how to measure fuel economy. Cheers.

Indeed. Even if there was a 5L per fill variation from bowser X to bowser Y on a 50L fill, it's still not a 100% increase in expected fuel consumption.

[spud75]

Just a quick update, tried disconnecting the battery overnight, didn't seem to make any immediate difference to mfd consumption readings, still showing silly numbers under even light acceleration and average numbers while cruising (between 7 to 10L/100km). Will wait and see what I get at the next tank fill.



no don't need to go to specific dealer. Townsville is closer, but I refuse to take a car back to them. We have a good relationship with the dealer in cairns so I would like to take it back to them.

I dont want to cloud the fuel measuring technique. But...may I suggest that you reset the average (2) counter on the MFD? This is a continuing average from the time you do a reset. You mention that cruising average is down to 7-10 now. Is this the instantaneous reading or the average (1) reading? The average (1) is from the time you start the car till you stop for more than 2 hours.

My first tank of diesel I averaged in the 13's. The car was delivered with 33km on the clock though. At 2500km the car should have settled somewhat.

And to ensure there are no outliers, you have obviously checked tyre pressures, you dont have fridge in the boot, or a layer of bricks, and square roof racks with a couple of ladders on them etc..... or doing a bunch of dirt driving more than usual.

I f all these check out, then it may well be an dodgy O2 sensor or something. I have had to replace both sensors on the DPF on my A3, but you will need a dealer check to check those out.

[ZokEE]

I dont want to cloud the fuel measuring technique. But...may I suggest that you reset the average (2) counter on the MFD? This is a continuing average from the time you do a reset. You mention that cruising average is down to 7-10 now. Is this the instantaneous reading or the average (1) reading? The average (1) is from the time you start the car till you stop for more than 2 hours.

My first tank of diesel I averaged in the 13's. The car was delivered with 33km on the clock though. At 2500km the car should have settled somewhat.

And to ensure there are no outliers, you have obviously checked tyre pressures, you dont have fridge in the boot, or a layer of bricks, and square roof racks with a couple of ladders on them etc..... or doing a bunch of dirt driving more than usual.

I f all these check out, then it may well be an dodgy O2 sensor or something. I have had to replace both sensors on the DPF on my A3, but you will need a dealer check to check those out.

usage off mfd is instantaneous readings. Only reason I have mentioned them is because I know what our previous 147 tsi octavia was doing under same conditions and this tdi is higher in every regard, never taken much notice of the averages as they don't match up with the averages from tank fills.

ours had about 30km on delivery too and pretty much did a 1400 km trip home the next day.

Tyres are good, no excess baggage either. No dirt driving, that's what I have a hilux for!

I'm still trying to organise time to get out to the coast, so no resolution in near sight.

[MGV]

When you did the 1400km trip home, if the fuel usage was indeed excessive, you probably would have needed to stop & fill up 3 times along the way. That motor should have you making it home with one refill & still half a tank left upon arrival.

I'm sure i'm not the only one thinking you are not reading short term average, long term average & instantaneous for what they are?

My averages are usually between 8 & 11 l/100km, but if i set it to instantaneous & floor it up a hill, it will read 49.9 l/100.

Still looking forward to the outcome...

[ZokEE]

I dont want to cloud the fuel measuring technique. But...may I suggest that you reset the average (2) counter on the MFD? This is a continuing average from the time you do a reset. You mention that cruising average is down to 7-10 now. Is this the instantaneous reading or the average (1) reading? The average (1) is from the time you start the car till you stop for more than 2 hours.

My first tank of diesel I averaged in the 13's. The car was delivered with 33km on the clock though. At 2500km the car should have settled somewhat.

And to ensure there are no outliers, you have obviously checked tyre pressures, you dont have fridge in the boot, or a layer of bricks, and square roof racks with a couple of ladders on them etc..... or doing a bunch of dirt driving more than usual.

I f all these check out, then it may well be an dodgy O2 sensor or something. I have had to replace both sensors on the DPF on my A3, but you will need a dealer check to check those out.

usage off mfd is instantaneous readings. Only reason I have mentioned them is because I know what our previous 147 tsi octavia was doing under same conditions and this tdi is higher in every regard, never taken much notice of the averages as they don't match up with the averages from tank fills.

ours had about 30km on delivery too and pretty much did a 1400 km trip home the next day.

Tyres are good, no excess baggage either. No dirt driving, that's what I have a hilux for!

I'm still trying to organise time to get out to the coast, so no resolution in near sight.

[ZokEE]

My averages are usually between 8 & 11 l/100km, but if i set it to instantaneous & floor it up a hill, it will read 49.9 l/100.

Still looking forward to the outcome...

Mine says 49.9 on half throttle taking off from standstill.

[kaanage]

As gldgti has said, let's all accept that the OP has done the right thing regarding tyre pressures, not carrying excessive loads, measuring fuel consumption by fill ups vs odometer, not running the car in Sahara type heat with the A/C on and windows open at 200km/h, etc

He has stated all of this in previous post so let us accept that the car has a fault and only discuss possible causes or else wait for him to proviide updates.

All this speculation about improper vehicle operation is a waste of bandwidth.

[Mysticality]

Foam can cut a bowser off.
I can usually get another litre or two in after bowsers first cut out.
I fill to the brim.

Agree 100%

Its using way too much fuel. I have the same engine, 225,000km old at this stage, stage 2 tuned and gets floored everywhere with big heavy brakes and all kinds of other fancy things that don't really help economy.
I track everything with Fuelly.
Worst number I've ever gotten was 8L/100 - after a day spent at Marulan Driver Training Centre doing hard laps of the track.
There's also a 12.5L/100 in there but that was a trip from the servo in town, to home, then back to the servo - turns out that takes 1L exactly brim to brim if I'm flooring the hell out of it! (Wheel spinning everywhere like a crazy thing - forgot wallet )

Terrence (Skoda Octavia) | Fuelly

[ZokEE]

So I got hold of an obd scanner, but only had limited time to play with it.
coolant temps are fine, so that can be ruled out.
Absolute throttle position seems to be giving some weird numbers, 83.9% with throttle fully closed, not quite sure what's going on there.
Only had time to stuff around driving to/from work on night shift, but finish work in two days so hopefully get time then.

[Mysticality]

Absolute throttle position seems to be giving some weird numbers, 83.9% with throttle fully closed, not quite sure what's going on there.

Mines exactly the same.
I doubt you'll find anything with the OBDII reader... Perhaps monitor fuel rail pressure?
Mine will idle around 3,800psi and at peak boost/4.8k rpm hit around 27,000psi

[gldgti]

The fuel pressure won't likely show any problem, unless it was low, which would seem unlikely.

[ZokEE]

Yeah, max fuel pressure 26580 psi, max MAP 36.7 psi.

[gldgti]

Yeah, max fuel pressure 26580 psi, max MAP 36.7 psi.

That 36.7 psi was a spike right?

I dont think the stock boost is that high - should be below 30. It will certainly spike under the right cercumstances, but I reckon it would be plateau-ing around 25 IIRC.

***EDIT*** can you confirm the MAP as gauge or absolute?

[ZokEE]

That 36.7 psi was a spike right?

I dont think the stock boost is that high - should be below 30. It will certainly spike under the right cercumstances, but I reckon it would be plateau-ing around 25 IIRC.

***EDIT*** can you confirm the MAP as gauge or absolute?

Can't say, that was just the maximum it logged. I had the laptop on the passenger seat and not watching it while going. Hopefully tomorrow I'll get a good go of it minus kids and other distractions.

[h100vw]

Not forgetting, if you are logging with VCDS that it adds ambient pressure which needs to be subtracted.

Gavin