I normally have my maxi-dot display set to show the single journey fuel consumption.

My commute is 11 mile each way made up of about 1.5 miles local roads with limit 30-40mph, 5.5 miles of dual carriageway at 70mph, 1.5 miles of busy dual carriageway typically at 50mph and 2.5 miles of local roads mostly 30mph but half a mile of 20mph.

From new I had noticed some significant mpg variations but since coming back from holiday 5 weeks ago which included motorway runs of 150 miles each way and now over 3500 miles covered I have watched the daily mpg carefully.

For nearly two weeks I was getting near to 60mpg each way and a couple of times on very clear runs over 60mpg.

Then one evening I had a DPF regen (as I noticed the heat). After this I was only getting just over 50mpg and a couple of times under 50mpg each journey for about a week.

The mpg then picked up to upper 50's for a few days before back to low 50's. I didn't notice a regen but assume one occurred. The last couple of days I am back to high 50's mpg again.

Of course I expect some day to day variation depending on traffic but I am seeing blocks of a few days with an average mpg variation of at least 15%.

I can understand lower mpg on a journey if the DPF does a regen. I could also understand if the regen did not complete so ran again the next journey but I have never noticed the heat on consecutive journeys or days.

Has anyone else noticed this?

Can anyone in the trade comment if the lower mpg for a few days after a regen is normal and explain why or if somehow the DPF regen is causing a problem e.g. upsetting a sensor.

Mine is better after regen more mpg

Mine is better after regen more mpg

Interesting as the opposite of I am finding.

Tonight as I pulled on the drive the computed single journey mpg was 62, the best ever. I didn't even have an exceptionally clear run. Last week 52mpg would have been typical.

This morning was 6mpg lower at 56mpg despite overall a better than average run but still around 5mpg up on last weeks typical readings.

I guess evenings will always be best as engine is warmer on the dual-carriageway section.

Interesting as the opposite of I am finding.

Tonight as I pulled on the drive the computed single journey mpg was 62, the best ever. I didn't even have an exceptionally clear run. Last week 52mpg would have been typical.

This morning was 6mpg lower at 56mpg despite overall a better than average run but still around 5mpg up on last weeks typical readings.

I guess evenings will always be best as engine is warmer on the dual-carriageway section.

66.7 mpg today on a 45 mile run was 69 until I gave it some beans, the higher figure around 60 mph on cruise air con on

Delta, I think the first thing to establish is how accurate your trip computer is being. I would recommend that you carefully brim the car at the next opportunity. Take your time over this to allow as much air out of the tank as possible. Then reset your trip mileage meter AND reset your trip mpg computer then just drive in your normal fashion. Leave the mpg trip computer alone and let it just keep logging your average miles per gallon until you next fill up. Empty the tank by at least half and then refill to the brim in the same way your did previously. Use the same pump if you can. Then work out your mpg by dividing the number of litres you've just put in the car by 4.54 to give you the gallons used. Then just divide the miles you have covered by the gallons used. Check your answer against the trip computer. It shouldn't be much more than a mile or two out if you've been careful with your brimming. If there is a big difference you will have a problem with your trip computer than can be checked and changed at the garage.

Very interesting - we've noticed week-long trends in the fuel consumption and indeed, delta925, we've had exactly the same experience. Ours is now a 2011 1.6CRTDI 105bhp elegance estate. I hadn't connected it to the DPF regen but that would make sense.

I have to say I'm a bit disappointed with the fuel economy generally on this car. I've got a very light right foot and would easily sometimes reach 70mpg on our 2006 1.9TDI elegance estate MK1 - but now struggle up to 60.

Very interesting - we've noticed week-long trends in the fuel consumption and indeed, delta925, we've had exactly the same experience. Ours is now a 2011 1.6CRTDI 105bhp elegance estate. I hadn't connected it to the DPF regen but that would make sense.

I have to say I'm a bit disappointed with the fuel economy

generally on this car. I've got a very light right foot and would easily sometimes reach 70mpg on our 2006 1.9TDI elegance estate MK1 - but now struggle up to 60.

Well you have not done a lot of mileage, the crtdi engine is

very tight and will not give you good mpg until at least a couple of 1000k on the engine, the 1.9 tdi engine is a fantastic engine but eventually your engine will loosen up, and you'll start getting better fuelly but it will take a while, I get 60-70 mpg but the engine does not like 70+ mph it will swallow fuel

Edited 27 August, 201114 yr by seboni121

Delta, I think the first thing to establish is how accurate your trip computer is being. I would recommend that you carefully brim the car at the next opportunity. Take your time over this to allow as much air out of the tank as possible. Then reset your trip mileage meter AND reset your trip mpg computer then just drive in your normal fashion. Leave the mpg trip computer alone and let it just keep logging your average miles per gallon until you next fill up. Empty the tank by at least half and then refill to the brim in the same way your did previously. Use the same pump if you can. Then work out your mpg by dividing the number of litres you've just put in the car by 4.54 to give you the gallons used. Then just divide the miles you have covered by the gallons used. Check your answer against the trip computer. It shouldn't be much more than a mile or two out if you've been careful with your brimming. If there is a big difference you will have a problem with your trip computer than can be checked and changed at the garage.

Hi Estate Man,

I have worked out the real mpg compared to average 2 from the maxi-dot a few times and the overall results are close enough to assume the sensors and electronics are fine.

However it is not really practical to try this over each block of a few days higher and lower mpg.

Ultimately I'm wanting to establish if what I am finding is for whatever reason a characteristic of a DPF regen and/or the 1.6 TDi CR in general or there is a fault that the dealer / Skoda need to investigate.

Very interesting - we've noticed week-long trends in the fuel consumption and indeed, delta925, we've had exactly the same experience. Ours is now a 2011 1.6CRTDI 105bhp elegance estate. I hadn't connected it to the DPF regen but that would make sense.

I have to say I'm a bit disappointed with the fuel economy generally on this car. I've got a very light right foot and would easily sometimes reach 70mpg on our 2006 1.9TDI elegance estate MK1 - but now struggle up to 60.

Hi,

Thanks for posting so I know I'm not the only one experiencing these spells of significant mpg variation.

As I've posted I have had them from new but thought maybe after everything settled down they might become less and perhaps eventually disappear but so far no sign of that.

I want to establish if this trend is to to be expected or is abnormal and I need to push the dealer / Skoda into the corner to investigate.

You have not said how many miles you have done so far but your overall mpg will gradually increase as the engine beds in.

I'm sure if now I went on a 50mile drive on clear open roads at steady 55-60mph started when I was in a good mpg spell and didn't get a DPF regen on the run I would get at least 65mpg.

My previous car was an Audi A4 with the 1.9TDi and now even with these mpg variations I'm getting an average of 3-4mpg more on my normal journey pattern. If I was always getting the mpg that I was in the good spells I estimate I would be getting at least 8 and maybe 10mpg more.

Also to me the 1.6TDi CR is not happy below 1500rpm so I ignore the gear change indications and I recall a post on here that someone got better mpg on a cross-country run keeping in 4th gear instead of using 5th.

Skoda quote max torque of 250Nm in the range 1500-2500 rpm. I'm now at 3700 miles so the engine is still not really loosened up but to me the start of the rpm range is rather higher at around 2000rpm.

We're just over 4000 miles. Driving it to Slovenia (from the Highlands of Scotland) soon so that'll loosen things up nicely ;o)

We're just over 4000 miles. Driving it to Slovenia (from the Highlands of Scotland) soon so that'll loosen things up nicely ;o)

Wow what a drive, great we will wait for your input after such a long trip

I used to have a Peugeot 307 with DPF; the information I'd seen was that during DPF regeneration extra diesel is indeed used in order to raise the exhaust temperature. I don't know if the VAG DPF's are similar.

Out of interest, with an 11mile commute it doesn't seem like you'll benefit from a diesel? When I was in one of the dealerships round here they told me that if they knew you'd be doing less that 10,000 miles they'd actively dissuade you from going for a DPF equipped diesel.

You can see the info here:

AA academy DPF info

"A surprisingly large number of people don’t take their cars anywhere near a motorway so passive regeneration is only going to be possible once in a blue moon. Soot builds up in the DPF and intervention from the ECU is needed to shift it. In the case of a filter without additive when the soot loading reaches about 45 per cent the ECU switches off the EGR and increases the fuel injection period so there is a small injection after the main injection. These measures help to raise the engine exhaust temperature to over 600ºC which is high enough to burn off the soot particles."

With an 11 mile journey your DPF is probably getting coked up and then going into an active regen to burn off the coking... Consuming extra fuel in the process and reducing MPG. If you were doing longer journeys passive regen could probably occur due to higher operating temperature.

It also depends on what type of driving is involved in the '11' mile commute. If it's mixed running where you can achieve 45mph plus for periods of time, it's should be ok and a passive will still occur. If it's slow traffic and mostly 30-40 mph it'll need a hand with an active regen. The amount of extra fuel injected is tiny and doesn't alter mpg by very much, but if the car for some reason is regening very often for whatever reason it will have a more noticeable effect. My sister does around 6-7 miles per day in her 1.6cr during the week and 20 miles at the weekend depending what's going on. Once a month she does an 80 mile round trip on the motorway. She's never had any DPF issues in the year she has had it, it just looks after itself.

When I ordered my car the salesman knew my basic daily journey but made no comment about about possible issues with the diesel while back then I did not even know DPF's were now standard fitment let alone the potential issues with short journeys.

I chose the diesel as I plan to keep this car for 10 years. Assuming the proportional difference in RFL remains it will offset the higher purchase price. Hence so long as diesel does not become significantly more expensive than petrol, and remember in 105PS setup the 1.2TSi prefers 98+ RON super unleaded, I will save on fuel plus the diesel ought to have a higher resale value.

Also realistically in a few years time I am more likely to be commuting more miles than less.

As in my first post about 50% of my commute is at around 60-70mph and another 10% at 40-50mph.

So far I have never had the DPF light come on but get a regen every couple of weeks.

I know because of 'eau de DPF', the heat and often the cooling fan running at the end of the journey. Also the displayed single journey mpg will be high and the tick over if waiting at junctions etc. will be 1000 rather than 800rpm.

For the next few days the displayed single journey mpg will then be 15+% lower than for the days just before the regen and 20+% lower than for the journey when the regen occurred.

The displayed long-term mpg is currently 53-54 and very close to my calculations.

I guess this will fall over the winter with the increased electrical load and longer time for even the water to reach operating temperature.

I am using mostly Shell Fuelsave diesel with odd fillups of Texaco, Total and Jet while apart from one tankful I kept have clear of the supermarkets.

It is all a bit of a scam environmentally really with respect to road fund license (much like the electric cars); the only reason you get lower tax is because of the DPF which probably has a pretty high cost of manufacture in C02 terms! Likewise the huge environmental impact of building 100KG+ of batteries. Not so much carbon-reducing as carbon shifting. A bit of a nonsense that the industry has come up with.

Credit to you though for the long-term view - so many people look at a car as a 2 or 3 year proposition...

I'm intrigued though by you mentioning that the MPG is then low for a few days afterwards. I'm really interested as I'm keen on the Greenline II which is DPF equipped, though my journeys are significantly different to yours. Does it gradually creep back up to "normal" MPG, or all of a sudden "switch" to normal MPG?

After mine goes through DPF my 1.6crtdi has very improved fuel economy ?

It is all a bit of a scam environmentally really with respect to road fund license (much like the electric cars); the only reason you get lower tax is because of the DPF which probably has a pretty high cost of manufacture in C02 terms! Likewise the huge environmental impact of building 100KG+ of batteries. Not so much carbon-reducing as carbon shifting. A bit of a nonsense that the industry has come up with.

I totally agree about environmental scams that while making a reduction in pollution at the point of use create pollution during manufacture. Often they also use up precious non-replaceable raw materials and of course energy is used and hence yet more pollution created to extract, process and transport them.

Specifically with vehicles if all the emissions systems were removed the fuel consumption would fall. I read somewhere that the changes required to bus diesel engines to meet next set of emission regulations will significantly increase fuel consumption ......

Credit to you though for the long-term view - so many people look at a car as a 2 or 3 year proposition...

My long term view is not by choice but funds. Normally I buy a 3-4 year old reasonable mileage car and keep for 5-6 years. Last year anything I looked at was either higher mileage or too high a price due to businesses, leasing companies keeping cars and private buyers all keeping cars longer so good lower mileage cars being in relatively short supply. With the VAT deal then keeping for 10 years ( or up to 120,000 miles if my mileage increases ) the average yearly depreciation worked out lower.

I'm intrigued though by you mentioning that the MPG is then low for a few days afterwards. I'm really interested as I'm keen on the Greenline II which is DPF equipped, though my journeys are significantly different to yours. Does it gradually creep back up to "normal" MPG, or all of a sudden "switch" to normal MPG?

The change back to better mpg following a DPF regen either after a few days of commuting or during a long journey is essentially is a step, or maybe a steep slope over a couple of days, not a gradual trend.

After mine goes through DPF my 1.6crtdi has very improved fuel economy ?

All I can say is the opposite of my experience .....

I wonder if after a regen I continued for at least 25 miles at a decent speed if I would get low mpg then better mpg, if I would miss the low mpg completely or if I would still get it on the next trip(s) .....

I know it would confuse 99% of drivers but a 'DPF regen in progress' light on the dash would be useful to us who understand what a DPF regen is.

(Admin - we need a puzzled emoticon something like a combination of these two )

B)My Greenline 1.4 increases fuel consumption slowly over a period of driving mostly in and around town with minimal duel carriageway use and learner drivers doing manouevres, etc, getting worrieingly low at one point (just under 40mpg) But I then drove to and from Legoland (Windsor) from East London, via M11, M25 and M4, where the consumption on returning, despite a few miles of very slow traffic, returned a little over 70mpg, fully laden and without checking the tyre pressures, which may have made a bit of an improvement! I guess with just me and correctly inflated tyres for faster roads, I would have had nearer to 75mpg.

So, I guess a proper run does well in cleaning out the engine and exhaust system, giving better long term gas/mileage.

Oh, and I am now getting a few miles under 50 mpg, with learners!

Delta, I'm wondering if there is an issue with your EGR (exhaust gas recirculator valve) after a regen. During regen the EGR is closed by the cars electronics to help raise the exhaust gas temp. The EGR can become a bit sticky when it's dirty and this may mean after regen it may be slow to go back to normal (if indeed it does). A sticky EGR can affect fuel consumption. To avoid this make sure you vary the engine revs and load often, be a bit heavier than normal with the gas now and again, and don't go everywhere treading very lightly on the gas. That will encourage better exercising of the EGR and make it less likely to sticky operation. I've dealt with sticky EGR's before on diesels although I have to say not on the CR1.6.

Edited 26 September, 201114 yr by Estate Man

Friday afternoon I had a DPF regen - 1000rpm on tickover, fan running when engine stopped plus the ' eau de DPF '.

At the weekend I only went into town which is 2.5 miles each way. The single journey mpg was 38mpg overthe 5 miles, normally it is well into the 40's.

Today arriving at work 48mpg when virtually always above 50mpg unless very heavy traffic.

Tonight I had to go somewhere so not a normal run and it would have reduced the mpg anyway but 47mpg.

The long-term average is now down to 52.8mpg too.

I went up to the dealers a couple of weeks ago to report both this and the clutch judder.

The head technicians comments after a brief drive with me were increased fuel consumption after a regen is normal and the clutch judder when setting off is not bad enough for them to consider a clutch change plus it still may go away although now over 4000miles .....

I have now had the car 6 months and I'll post my various comments separately when I get a few minutes.

Estate Man thanks for your comments.

In the morning nearer the end of the journey once the engine is warm it is very difficult to make it work because the traffic.

Other than keeping in a lower gear so the revs are higher not that much easier in the evening, only really one place where if clear ahead I can accelerate hard and then a 50mph limit.

The one location where I could floor it if clear ahead is the slip road up to the dual carriageway on my way to work but since only just over a mile from home the engine is still cold hence not good to do it there.

I do try not to change up too early regularly holding 2nd in particular so the engine at least briefly gets to around 3500rpm regularly but of course still relatively lightly loaded. I'll active seek opportunities to get the throttle open wider. Maybe if I can do it in an evening without upsetting other traffic slow down a little and drop back then drop to 4th and accelerate hard gaining 10mph.

My only comment about an EGR valve issue is would the pattern be so consistent right from 0 miles?

MRGF,

The greenline with the 3pot engine looks to be significantly more economical at motorway speeds. I have done four 100+ mile runs mainly on dual carriageway / motorway at 70mph and each time 60 +/-1 mpg was displayed for the journey and that is with one person.

I don't envisage another 100+ mile trip until well into next year, it will be interesting to see if the mpg improves significantly as by then the car should have done 10000 miles.

Estate Man thanks for your comments.

My only comment about an EGR valve issue is would the pattern be so consistent right from 0 miles?

In short, no. Not unless your EGR was faulty from new and that's unlikely, unless it has a defect causing it to stick when very hot...as in after a regen.

Ultimately I am not assuming any other 16.TDI CR would deliver significantly different mpg to my car on the same journey pattern.

However given these results so far

http://briskoda.net/forums/topic/215054-first-decent-mpg-test/

it would be interesting to swap cars for a month.

I was late leaving work tonight and with roads a bit quieter on dual carriageway I kept to 60mph and mentally averaged the instantaneous reading and reckon low 60's certainly not 70+.

What I should have done is reset the computer so will try to remember next time a similar opportunity.