I've had my PD140 for over a year now. Done 30K and always seen the first 90 miles of the Monday morning motorway commute see the computer saying I'm

averaging just short of 50mpg, which I'm happy with.

I've not changed my route or driving technique, traffic, but recentally noticed that on the same stretch my economy is struggling to get to 44mpg.

I usually arrive at work sitting at 55mpg average, but now its struggling to get to 48mpg, the latter part of my journey now sees far less stop-start traffic as well.

Is there anything that could be causing the economy to drop ? I have noticed that the economy as per usual on slower trip during the week, only seems to

be when the speed picks up....

Could this be a MAF issue ?

has the air filter been changed yet?

Yes change the air filter, VAG's recommendations for the intervals are far too long (40k)

Cheers guys.

I'll need to have a look and see if its been changed. It was just in for a service a couple of weeks ago, so I'll check the book first.

Don't trust the book, whip it out and have a look, only takes 5 minutes

Check the tires pressure, it makes an incredible difference when they are out of the specs.

BTW, I prefer to have them in the higher recommended levels (not the highest but almost).

Air filter should make no difference to fule economy - the MAF will just restrict the max power if the air filter is restricting the flow.

They probably filled it with 15/40W oil instead of good quality 5/30W. (gives a 3 - 5% difference in economy)

They probably lowered your tyre pressures. (can give 5%+ difference in economy)

Have they adjusted your handbrake - maybe too much and theyre binding a bit - check the temperature of the disc - if they are stinking hot then they are not fully released.

Air filter should make no difference to fule economy - the MAF will just restrict the max power if the air filter is restricting the flow.

They probably filled it with 15/40W oil instead of good quality 5/30W. (gives a 3 - 5% difference in economy)

They probably lowered your tyre pressures. (can give 5%+ difference in economy)

Have they adjusted your handbrake - maybe too much and theyre binding a bit - check the temperature of the disc - if they are stinking hot then they are not fully released.

A clogged air filter does make a big difference in fuel economy as I've found many times.

I agree about checking tyre pressures, but putting 15w-40 oil in the car would be madness and certainly worth a shouting at for many many reasons.

Personally, I'd put the air filter at number 1, especially as it sounds like you've done 30k miles in it.

30k miles means that it won't have been changed under the skoda service recommended intervals, but will be getting towards the pretty blocked stage.

Dealer should be able to supply you one for about £12 and fitting is a case of removing a few screws and swapping the filters over, then doing the screws up again.

I always change the air filter on my cars every 10K / 1 year, they look pretty mucky after that time so 40k can't be a good idea and it will cost less than a tenner.

Tyre pressures

Air filter

MAF

In that order really. If it were my car, I'd probably run a diagnostic scan with VCDS as well, to see if anything were amiss.

I just checked the invoice for the service last week @ 93k.

According to the invoice for the last service it didn't have an air filter this time, and according to the service book, it didn't have an air filter last time @ 73k, so I'll need to check the invoice for the 73k service.

Either way its not had an air filter in the past 20k miles.......... if the invoice says it didn't have an air filter, at 73k either, then its not had one since 55k !!!

It has had three pollen filters mind you !

Going to try and stop at the dealer on the way home and pick one up... I guess you just need to remove all the screws holding the

airbox together ?

Thanks for all the replies....

Tyre pressures - all ok.

Brakes - none binding "now"...... just had two new front calipers, one two months ago, one last week.... thought that was the cause !

Going to look at the air filter then the MAF. hopefully get an air filter tonight.

I hope its been serviced with the correct oil, as it was serviced by an "approved" Skoda service agent...... aka a VW dealer !

Car is on longlife 20k service intervals and has been serviced on the button each time.

Blimey! Yep, just pop the screws off and then lift the cover off. If you don't manage to grab a one straight away, take the old one out anyway and give it a shake and vacuum it. Be gentle with it though, as it's been in there that long, it might well start to disintegrate!

Might be quite useful doing it this way actually, then see if your economy is any better tomorrow

I found on the MK I that at near to 40k miles the filter was more like a block of soot than a clean filter.

The MK II has this issue less, but after about 10k it's starting to get a bit dirty. By the time it's at 20k, a filter swap out for a new one will give an MPG improvement.

Seems strange to me that they don't spec it as a changeable item at each service. They usually like to swap things and charge people, they might as well change something that actually might need it!

Seems strange to me that they don't spec it as a changeable item at each service. They usually like to swap things and charge people, they might as well change something that actually might need it!

Well thing is it will run until 40k/60k (vehicle dependant) without causing anything to go bang in the short term.

This means the costs for fleet managers is kept lower and lets face it the fleet is a volume market.

It also means the running costs to an end user appear to be cheaper.

So that £200 basic service then becomes + an air filter + an early fuel filter + plus this, plus that etc if you want to keep the parts on a short schedule.

Edited 11 August, 201015 yr by cheezemonkhai

Picked up a new filter after work, seemed a bit steep after what people had quoted.... £15 inc. VAT.

Changed it over earlier on, so I'll see if I notice a difference tomorrow. The old one was fairly dirty, but I doubt its been in there 40k....

must have been changed at the last service, but that was still 20k ago !

Edited 11 August, 201015 yr by swil00

Have you got a part no. For the filter as I think I might change the one in mine as I doubt that's been done on it's last service.

Incidentally anyone know of any performance panel filters? Are they the same as for the TFSi engine or completely different?

Have you got a part no. For the filter as I think I might change the one in mine as I doubt that's been done on it's last service.

Incidentally anyone know of any performance panel filters? Are they the same as for the TFSi engine or completely different?

IIRC The filter is different on the TFSI as that's on the engine not in a separate airbox as on the TDI.

Part number for an air filter should be in the Octy II handy part numbers sticky.

Cheers

Seems strange to me that they don't spec it as a changeable item at each service. They usually like to swap things and charge people, they might as well change something that actually might need it!

I can assure you that unless the car has been remapped, the only effect a dirty/blocked air filter is to restrict maximum torque and power. I.e. performance will drop but fuel consumption will not. Thats the sole reason for a MAF sensor - to ensure compliance with Euro emission regs. - it will not allow overfuelling due to restricted air flow.

Of course all that goes out the window when you remap or "tune" the engine.

I can assure you that unless the car has been remapped, the only effect a dirty/blocked air filter is to restrict maximum torque and power. I.e. performance will drop but fuel consumption will not. Thats the sole reason for a MAF sensor - to ensure compliance with Euro emission regs. - it will not allow overfuelling due to restricted air flow.

Of course all that goes out the window when you remap or "tune" the engine.

Surely if you restrict power & torque then the car is using less power and torque to move the same mass therefore will affect fuel consumption.

Or does that not matter?

Surely if you restrict power & torque then the car is using less power and torque to move the same mass therefore will affect fuel consumption.

Or does that not matter?

It would only restrict maximum torque (at the top end of rpm) and maximum power (which is a product of torque and rpm). Most people dont access this part of the power curve in normal day to day driving. In some cases I imagine it may actually cause the economy to improve slightly due to restricting operation within a more efficient area of the power/torque curves.

I personally feel that they put the wrong oil in - longlife III oil is 5/30W with ECO (low friction) characteristics. I bet they banged in Quantum Platinum 505.01 5/40W - thats what my dealer uses "because its cheaper than the stuff they have in the workshop barrel" - their words, not mine.

Edited 11 August, 201015 yr by xman

I can assure you that on an unmapped car, with a pretty dirty air filter the MPG does drop off. A change of filter gave a good increase and this has happened more than once.

As an example if you were to try following a car at night with a dirty filter, then swapping the filter for a new one. You'll see there is less soot coming from the pipe.

Since soot is unburned fuel or incomplete combustion, then there must be something causing the issue as the dervs always run with an excess of air.

The turbo cuts in and hits this limit on full boost, hence soot, so there are factors under which a car with a MAF will not fully burn the fuel.

Incidentally anyone know of any performance panel filters? Are they the same as for the TFSi engine or completely different?

As Mark says, they're different Carl. But the same across PD140 applications - so Golf 5/Jetta etc. Also the same as the 1.4TSI unit incidentally.

I've just ordered a Pipercross one.