125tdi woeful fuel economy, help!

[ZokEE]

Hi Guys,

Before i start, the reason I am posting here and not taking the car immediately back to the dealer is that we live 1400km from the dealer.

Long story short, bought a new skoda superb outdoor with the 125tdi engine. On the 1400 km drive home i made sure to vary road and engine speed/gears and not sit on constant rpms. mfd indicated average of around 8L/100km which i wasn't too distressed about given how i was driving it.

Since being home I've been shocked at how bad the fuel economy has been. First tank fill was avg 13.5L/100km and second fill was avg 11.2L/100km. We do alot of frequent short trips, but engine always reaches running temperature on any given drive, shortest trip usually about 10 minutes, longest maybe 30 mins? We have had the car for 2 months now and put about 2500 km on it, the avg usage seems to be dropping with each tank fill, but is still obviously twice what it should be.

Coolant temp never goes over 90, but I've seen oil temp up to 105. Never any warning lights, no limp mode, but occasionally when i turn the car off and hop out it feels awfully hot around the front of the car and the thermo's continue to run for an extended period after the car has shut off (sometimes >5 mins). On occasions there has been a slight burning smell from the engine bay. I know what overfuelling does with egt's and i'm more than a little nervous something is going to die very shortly.

I have already contacted the dealer, who has confirmed that it should obviously not be using that much fuel and obviously said to bring it back so they can run diagnostics on it.

With mine and my wife's work schedules and two young kids in the mix, it's looking like i wont be able to get back to the dealer for at least another month, so my question is mainly is it worth acquiring a VCDS and would i be able to log any data/parameters that would tell anyone anything useful in the mean time (sensor gone haywire etc) or am i better off just waiting and taking it back to the dealer? I'd prefer not to melt it on the drive back there and may have to look at having it transported.

Sorry for the long read, any help would be much appreciated.

Cheers, Steve.

[Umai Naa!!]

What's the ambient temperature been like?

Will have a noticable effect on fuel economy.

[vdubmotorworx]

The heat lately has been increasing fuel consumption and your short drives will mean dpf regen all the time explaining excessive heat from engine and poor eco

[kaanage]

occasionally when i turn the car off and hop out it feels awfully hot around the front of the car and the thermo's continue to run for an extended period after the car has shut off (sometimes >5 mins). On occasions there has been a slight burning smell from the engine bay. I know what overfuelling does with egt's and i'm more than a little nervous something is going to die very shortly.

Yep, that's the DPF going through a forced regen which is a total PITA and wastes fuel.

But hot conditions shouldn't be the cause of excessive fuelling and soot as we drove back from Adelaide after New Year's when the temp was around 40 deg C and over the 750 odd km, our 103kW CR MkVI Golf was getting around 5l/100km loaded up and with the aircon on and even around town we always get sub 7l/100km.

Let us know what the dealer finds

[benough]

I'd say stick it out. Just keep driving it "well" until you can see the dealer. A VCDS won't give you any magic answers as to what it's eating fuel, so unless you want one for other tweaks, don't bother.

[ZokEE]

So I should be expecting a near 100% increase in fuel usage under the given conditions?
we moved from a 147tsi octavia, number 1 for space and 2 for fuel price/consumption. I used to drive the tsi like I stole it and rarely saw 13L/100km, and it saw two summers with temps over 45 degrees C.
In the mfd under instantaneous fuel consumption I only ever saw 40-50 L/100km indicated in the tsi with the foot buried in 2nd or 3rd gear, whereas the tdi is regularly showing 49.9L/100km when pulling away from lights etc at half throttle.

[benough]

Yeah.

My 125TDI is the version before yours and I floor it everywhere. Worst I can get is 8L/100km.

As you said, your location and free time is against you atm, just keep driving it till you can get there. Then maybe haggle for a discount at next service for the money you wasted in fuel

[Greg Roles]

Drop me a pm, I can loan you one.

Very odd, and unless a new DPF is playing up, even short trips will take a while to start loading up prematurely. My Yeti gets about 800 between regens, which I might add is almost invisible to the driver, and to Vag Com in the Mk6 compared to the PD Mk5.

My gut feel is the DPF differential pressure sensor is either needing calibration, or is playing up, and that would have it regen-ing too often, and would run that sort of economy. The yeti, albeit the piddly 103 is getting 6.7 all day every day, and its a heavier car with worse aerodynamics.

It would pay to actually track kms between fills, as MFD displays are quite inaccurate, especially at first while they gather averages over several weeks before being close to right, I actually disable my averages and instant and just do the trip meter.

[Ryeman]

I tend to think if you refuel in the cool early morning and use it during the heat of the day .....as fuel expands with heat you should get better economy. If you do it the opposite way you'll get the opposite result.
Each 'charge' takes into account the air 'density' via sensors and adjust the fuel requirement appropriately
Also hot air being less dense gives lower aero drag so in fact economy should be BETTER.
But max power will be REDUCED in high temps....don't confuse the two.

[Greg Roles]

Monitor the oil temps, you will see 102-109 under normal driving, and +10 degrees during regens, so more like 115-120.