Adjusting driving style to avoid clogging inlet and EGR?

[WesBrooks]

I've a 2 litre 2009 170bhp Skoda Superb that I use for commuting and get do high mileages compared to Joe Blogs. I've always recorded brim to brim mileage and fill levels just to keep an eye on costs and have an extra advanced warning of anything heading towards the tits-up side of the spectrum!

 

In the past I've been able to get high mpg figures (55 on the tank average, and one 700 mile tank full with a 55l fill) between the quoted urban and extra urban when on motorway traffic that was limited to 50 by average cameras. I guess a lot of this was slip streaming. After a couple of months of driving like this the car became unhappy and often stalled and refused to start until temperatures dropped below 65C and the everything was as if nothing had happened. Nothing showed up on the computer and DPF issues would have shown up as there are plenty of sensors on that. The general consensus is probably EGR getting a little clogged up, but it is an pain of a job to get to, so not worth attempting until confirmed. I swapped my commute to a longer faster route and the car seems to have cleared itself. MPG average for tank full is now more like 45-48 brim to brim. Reduction in MPG mainly down to a 5mph increase in target cruise speed from a GPS validated 65 to 70.

 

While modern diesels seem to be able to be driven comparatively economically for a given maximum power of the engine, it appears as if even with motorway miles unless there are a little higher up their % loading the EGR system and inlets tend to clog up.

 

So. Main question is when plodding along in slow, but flowing traffic at say 50mph which gear would be best for reducing the rate at which everything blocks up? My guess has been to drop to a lower gear which would keep the revs and airflow up, but the ECU would probably reduce the weight of fuel per shot as it doesn't need the same amount of energy from each combustion event. Higher gearing would slow the engine and airflow down keeping the hot stuff in the cylinder longer, but in turn any requirement to speed up would require much more torque due to the lower engine speed and therefore would likely run toward the rich end of the spectrum without getting much acceleration.

 

Thoughts? I'm tending towards keeping the engine rpm around 2000 when holding a speed for a long period of time but would be really interested to see if anyone knows of some driving style advice that is a little more in depth than the standard generic advice for economic driving!

[WesBrooks]

From internet searches I've found so far responses generally say avoid cheap fuel and driving style advise varies from 'you can't do anything about it, it's just a time/miles issue' to keeping the revs up.

 

Not found anything that really shows a detailed study.

 

It's a result of trying to get the emissions within limit (along with their cheat ECUs ;-) ) but 25,000 miles per annum (thankfully less than it used to be) in a petrol isn't too appealing. Like for like swap with the now 1.4 petrols with cylinder deactivation would be about the same on fuel costs but the 1.6 TDI eco models of the same age would still have the fuel costs of the 1.4 petrol beaten.

[psycholist]

I would continue to use the recommended gears for cruising but give it a couple of full throttle runs to the red line every week when the opportunity arises. This means all the moving parts in the turbo/EGR should get cycled through their range of motion, stopping deposits from building up in the way of the moving parts. Once you only do it when the engine is at temperature and drive it gently for a few minutes before shutting it off, the engine will run better for it.

[WesBrooks]

No gear recommendation display on my car. I have found these to generally tend to favour MPG over all else.

 

Fair point on the flat out acceleration once in a while.

[Ootohere]

WesBrooks, does those advising to avoid cheep fuels say were others that want 'much cheapness' can purchase them, 

or are they just meaning Supermarket filling stations that are buying fuel from multinational refiners and importers that sell billions of litres of diesel in the UK ?

[chimaera]

Towards the end of your commute, find a spot where you can slow down to around 30 km/h and then gun it in 3rd. It should hit the redline around 130 km/h. The extra fuel use won't impact much on economy but it'll blow out anything lodged in the exhaust during the trip.

[WesBrooks]

4 minutes ago, Offski said:

WesBrooks, does those advising to avoid cheep fuels say were others that want 'much cheapness' can purchase them, 

or are they just meaning Supermarket filling stations that are buying fuel from multinational refiners and importers that sell billions of litres of diesel in the UK ?

 

As far as I'm aware the refiners don't just sell one grade of petrol and diesel. This is evident by the performance differences between regular and performance grades on the same forecourt. As far as I'm aware buyers from these refinerys are able to specify levels of additives that can increase the performance or cleaning ability of the fuel. All that said BP's top spec diesel didn't fair too well in the last test I saw online.

[Ootohere]

Sorry you might be talking Diesel & Diesel with Additives / Detergents,

 and then Premium Diesel like Shell V-Power with higher Cetane.

 

Then Petrols come in 95, 97 or 99 Octane in the UK.   So no petrols are not all the same, but Diesel on sale meets the Minimum Standard before additives are added.

ie. The same Diesel stock.

 

BP has a new Formulation for Premium Diesel so tests done before 2016 and since might be different, 

then they have different formulations in other world regions.

Edited 1 February, 2017 by Offski

[WesBrooks]

Yes. At least on the same brand pay more and it's Octane/Cetane levels will improve and there is likely to be more additives that focus on cleaning or lubrication. Yes, the bulk fluid is the same but as with many things a small addition on the bulk can have a notable effect on the overall performance (economy, peak power, cleaning...) of the engine.

 

It is my understanding that the supermarkets skimp on cleaning and some of the other additives that premium fuel brands add, but unfortunately other than the octane/cetane levels there isn't much the layman can do to compare the specifications of the fuel other than seat of the pants.

[WesBrooks]

This is risking running off topic here. I am interested in what I can do to reduce the build ups and a few of the comments have helped remind me to thrash it from time to time!

 

With regards fuel, I run a premium brand and swapping to a supermarket or other fuel is unlikely to reduce build up unless someone has news that Shell VPower has terrible carbon buildup?

[CWARD]

Using supermarket compared to super duper premium fuels will have little effect. The main culprit for clogging up the EGR is down using a diesel for short runs that doesn't allow the engine to warm up enough. The exhaust combined with the fine amount of oil that comes in the compressed air from the turbo makes a gloopy mess that sticks to the valve and builds up until something fails. Higher RPM's help in moving the air/exhaust through the EGR but on a cold engine not advisable. If your journeys are short with lots of stops and starts the only sure fire to minimise EGR failure is to sell your diesel car and buy the petrol one you should have got in the first place. 

[WesBrooks]

2 minutes ago, CWARD said:

Using supermarket compared to super duper premium fuels will have little effect. The main culprit for clogging up the EGR is down using a diesel for short runs that doesn't allow the engine to warm up enough. The exhaust combined with the fine amount of oil that comes in the compressed air from the turbo makes a gloopy mess that sticks to the valve and builds up until something fails. Higher RPM's help in moving the air/exhaust through the EGR but on a cold engine not advisable. If your journeys are short with lots of stops and starts the only sure fire to minimise EGR failure is to sell your diesel car and buy the petrol one you should have got in the first place. 

 

25,000 per annum minimum. Mostly commuting, vast majority of that on motorways. Not yet had DPF issues. Got car with 102k on the clock now has 228k. I always treat the car easy until the temp needle has settled at the 90C. I'm trying to adapt my driving style to give best chance of reaching 300k with little drama. Replacing the car now when I have no repayments on it and it has minimal value makes little financial sense. It'd take about 3 years to cover the costs of swapping to an £8k second hand greenline model.

 

I'm interested to here the comparative merrits of a driving style that advocates getting into 6th as soon as possible in comparison to one that favours picking gears to keep the revs near 2000 when stuck in flowing traffic at 50. Yes the engine is running faster and pumping & friction losses may be higher but I think the leaner mixture would produce less soot, and so clog less. But, I don't know when the EGR comes into play. If this is it's ideal opening conditions then I may be making the situation worse as I understand the EGR to be about reducing NO emissions and it has a detrimental effect on particulate emission

[WesBrooks]

Buying a petrol when I bought this car would have cost me far more, and I don't think petrol engines last as long meaning it would have needed to be swapped out sooner too. The recent 1.4 petrol with cylinder deactivation are on a par with my car running cost wise, but that's not comparing like with like and running the modern smaller diesel would save more still.

[CWARD]

The EGR recycles exhaust gases back into the inlet which creates a cooler combustion which reduces Nox emissions. 

 

With the driving you describe I wouldn't think you're are likely to get EGR problems so I wouldn't worry about it. .

 

As you are not doing short stop start journeys then my comments about buying a petrol don't apply. 

[Ootohere]

Sorry for going Off Topic, but i really am interested in this 'Cheap Diesel' people talk of, because lower price does not mean inferior.

Detergents in Fuels can be an issue, Additive Packages,  crap added by Wholesalers / Big Name Retailers.

 

So what Premium Brand do you use, because some like ESSO get their fuel supplied in some areas of the UK by the same Supplier that produces and wholesales Supermarket Fuel.  (But to ESSO spec, ie Diesel.)

[WesBrooks]

Please start a new thread if you want to discuss fuel.

 

This will make the information you uncover in your thread easier to find by other people searching the forum at a later date.

Edited 1 February, 2017 by WesBrooks

[Ootohere]

?

Is it so difficult just to say what Brand of Diesel you use since that is very relevant.

Not another subject you mentioned 'those that say dont use cheap diesel'   

Many do not know where their fuel comes from or when the Winter Spec diesel gets into the filling stations, 

in you area that is earlier in the winter than further south.

 

There are 3 other Fuel threads running now, the EGR / DPF not even getting mentioned, 

Driving style is important, but the major failures some are having with DPF's and the Retailer of the diesel is important.

(getting covered in a rather odd way by the Motoring Press, you might think they are trying not to upset major advertisers...)

Edited 1 February, 2017 by Offski

[WesBrooks]

I mentioned Shell V Power earlier. Sorry I wasn't a little clearer. I use Shell V Power. The reason why I'm avoiding the subject is there is no obligation for the fuel providers to detail what they include, and so no guarantee what they are putting in today is the same as tomorrow. This is keenly demonstrated by it not being obvious when the winter fuel is in the pumps.

 

Financial effects are easy to work out.

 

Assuming £1.1/l for budget and £1.35 for premium then for every 34k miles covered I would save the £800 the EGR and Intercooler service would cost me. Assumes 0.25 per litre cost saving, 48mpg and 4.55 litres per gallon...

(800 * 48) / (0.25 * 4.55) = 33758.24....

 

The cost difference would pay for a £15 bottle of additive every 630 miles which for me filling up at the beginning of the reserve is one and a bit fills.

 

Cost difference for a 50 litre fill is £12 which works out as costing me £592 more per year with an annual diesel spend of £3200. If that is saving me the inconvenience of one break down a year - which would hike my recovery membership - then I'm absolutely happy with that, particularly if that break down was injectors which would likely expensive enough for me to have to consider replacing the car as there is no guarantee that the rest of the car would last long enough to warrant the spend on the injectors. Many people on here will be forking out lease hires of £200+ per month just to have use of (not own) a newer car to avoid that dreaded breakdown. My choice is costing me around £49 a month as depreciation is next to zero now it has so many miles on it.

 

All of this ignores the advocated economy benefits of the premium fuel which would skew the numbers toward the favour of the premium fuel.

 

Now that is in perspective you can see that I have chosen my fuel to maximise the life of the car. While some may argue choosing premium will have little effect on ultimate life I doubt any one will argue that budget fuel will make my car last longer, or have better performance.

 

What I'm interested in doing is extending that way of thinking to the driving style of my car too - hence the topic title. I suspect that at low load (eg 30-50mph) then dropping to sixth when there are no hills or acceleration requirements may be the most economic choice just based on fuel usage, but I fear that this will have detrimental effects on the ultimate durability of the engine. This is something that VAG don't care a jot about at the sort of mileages I'm clocking up as they'd much rather my car fail forcing me to buy a new one as no one would be surprised to hear a 228k+ mile car has met it's demise and therefore cause VAG group no ill effect on it's reputation.

 

 

[Ootohere]

I would never have a Euro 5 Emissions TDI due to the total hit or miss with the EGR / DPF, but once i had driven a Euro 6 2.0 TDI/SCR /DSG i was hooked.

Thinking was this would be the last diesel i would have but my mind is changing on that now.

 

It is just a 150ps SEAT Alhambra i have but having tried the 184ps i knew it would suit my needs.

Personally i think VW or SEAT have this engine and gearbox combination just right. 

The DSG with Paddles, Stop / Start, Auto Hold & Electric hand brake all of which i previously seriously distrusted. Now driving anything else seems just a PITA.

 

The cars was new in November but i tried the first 1,000 miles with Tesco Diesel, then Shell for 1,000 & then Shell V-power Nitro & now it is getting 

which ever is cheapest where i am at the time & mostly Tesco for the points but also Sainsbury's & Asda, but i am avoiding Morrison's.

 

I hope you get your 300,000 miles and more easily.

Good oil used is as important as the fuel with Diesels IMO and the driving style, and yours seem to be spot on.

[BoxerBoy]

2 hours ago, WesBrooks said:

This is risking running off topic here. I am interested in what I can do to reduce the build ups and a few of the comments have helped remind me to thrash it from time to time!

 

With regards fuel, I run a premium brand and swapping to a supermarket or other fuel is unlikely to reduce build up unless someone has news that Shell VPower has terrible carbon buildup?

 

I think you're right on the button there.

 

It seems you are covering a reasonable mileage and just need a few miles occasionally at higher revs to keep the hot bits hot.

 

My regular miles have reduced so I sometimes simply drop down a gear (or 2) for a stretch of motorway to give things a blow at 3,000 RPM or more.

The short term increase in consumption is insignificant.

[jafo]

Try to change your driving style to quick acceleration and then cruising speed. And quick overtaking few times a day - instead of trashing once a week.

How often do you have regen?

[WesBrooks]

How do you notice the regens? Guess I could search this forum but never had anything indicating a regen on the dash.

[chimaera]

The engine's idle speed will increase to around 950 rpm during regen and you might notice the gear suggestions being lower than usual e.g. 5th when it might normally suggest 6th. Otherwise there's no telltale.

[SuperbTWM]

1 hour ago, chimaera said:

The engine's idle speed will increase to around 950 rpm during regen and you might notice the gear suggestions being lower than usual e.g. 5th when it might normally suggest 6th. Otherwise there's no telltale.

 Even then, when the weather is really cold, I have noticed the high idle speed stay high to try and keep heat in the engine until the car shows maybe 70-80C on the temp gauge so its even harder to tell.

 

Regarding the EGR valve, they are quite prone to failing early, sometimes in the warranty period, and I personally think this is due to more to a poor design rather than clogging up. I've seen the state of some of the intakes on my previous diesel cars at well over 100k and they havn't been too bad compared to the the horror pictures you see of blocked egr valves on the internet that may be from countries where the diesel isn't as good.

Edited 1 February, 2017 by SuperbTWM

[chimaera]

4 minutes ago, SuperbTWM said:

 Even then, when the weather is really cold, I have noticed the high idle speed stay high to try and keep heat in the engine until the car shows maybe 70-80C on the temp gauge so its even harder to tell.

Yes, but if it's up to temperature and still idling that high then it's very likely to be a DPF regen.