FAQ: Diesel engines and DPF

Frequently Asked Questions
david sunderland
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Joined: Fri Mar 17, 2017 12:47 pm

Post by david sunderland »

My mini did the same as hounds car drive a short distance to warm engine only... not radiator ........and fan came on and noise came from Exhaust and a smell mini said it was the dpf cleaning itself. in the 3 years 20 ooo miles had no problems and I only do short runs...but I do drive at over 2000 rpm regardless at what comp use tells me change up for eco... that way engine will clean itself engines need to rev and work.....if your diesel fails. MOT on emissions take for along run to clean it out before taking it back also stick a cleaner through....
Qashqai tekna 1.2 petrol dig 6. 3. 17. gunmetal grey. glass roof m\ t...............now RENAULT KADJAR GT 160 BHP same as the QQ same car

TheStig
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Joined: Wed Sep 23, 2015 4:39 pm

Post by TheStig »

Hound wrote: Wed Jun 14, 2017 11:40 am Occasionally after a short journey in ordinary temperatures, the fan comes on when the engine is stopped, and stays on for several minutes, despite the engine not appearing to be especially hot. I've always assumed this had something to do with regeneration. I've never noticed any change in performance.
Mine does this too. Fan stays on for several minutes (and quite loud too) after short journeys on cold days. I assumed it's due to a faulty temperature sensor. Hopefully that's not the case and it's due to the regeneration.
65 plate 1.6dCi 130 Xtronic N-tec+ in Gun Metallic
gvmdaddy
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Joined: Thu Jun 19, 2014 11:28 pm

Post by gvmdaddy »

DanDan wrote: Tue Jun 13, 2017 10:58 am Hi

Fist time I've had a Diesel (QQ 1.5 J11 model) and I've been reading with interest the views/facts/opinions on the DPF.
Having read the posts, and getting 45 MPG around town for the past 6 weeks, at what point if any should I be concerned?
I'd appreciate any input or reference what MPG or fuel efficiency you get with a healthy/unhealthy DPF.

Thanks, Dan
No need to be concerned about the dpf. The qq monitors the state of the dpf and initiates a regeneration process when required. This is all done automatically. No extra noticeable noise or smell whilst driving. You will notice a slight increase in fuel consumption whilst regenerating, but its only for a few minutes and is very infrequent. If you turn the ignition off during a regeneration, then you may notice a slight sulphurous smell oitside the vehicle. The regeneration does not continue with the ignition turned off, but if the engine and turbo are particularly hot then the fan may run on for a couple of minutes to prevent overheating of the turbo. It is also suggested to idle the engine for a couple of minutes after a long run to help cool hot components. On restarting the car the regeneration will start again until tge dpf is cleared, again only a few minutes. On tge old qq (j10) it was recommended to give the car a short motorway run once a week or so to get heat into the dpf to burn off the offending soot. There is no such requirement on the new qq (j11) as it is fully automated, and yes, it does work, and well. As your car ages the mpg should get better, with urban and mixed runs giving you 55mpg and long runs upward of 75 +mpg. Round town, if you use your speed limiter to stick rigidly to 30mph and stay in 3rd gear, your mpg will maximise. 40mph limits....stick in 4th gear still using your speed limiter. On motorway runs the best you can achieve is using either cruise control or speed limiter and sticking at 58 to 60mph, this can result in mpg of 80 to 90mpg.....I have managed it a number of times, particularly in warm dry weather.
DanDan
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Joined: Thu May 11, 2017 12:52 pm

Post by DanDan »

Hi gvmdaddy

Thanks for the comprehensive answer and explanation of the processes.
You've put my mind at ease.

Thanks, Dan
Deleted User 3871

Post by Deleted User 3871 »

I'm thinking its most likely you were on a slight downhill, wind behind you etc. I can bet if you turned around & went back in the direction you came the mpg would be 1/2 of what you are quoting. So yes, it may be theoretical, but in 99.99% of situations you not going to get anywhere near 80 - 90 mpg.

So guys, dont get to excited at 90mpg, its a goal to aim for, but in reality your not going there. Also if you are doing 58 - 60 mpg indicated on a motorway your going to get overtaken a lot by lorries and buses (its the speed i tow my caravan on a motorway). Its not the nicest of experiences as there are a lot of dicks about and they dont drive to well.
gvmdaddy wrote: Wed Jun 14, 2017 1:34 pm On motorway runs the best you can achieve is using either cruise control or speed limiter and sticking at 58 to 60mph, this can result in mpg of 80 to 90mpg.....I have managed it a number of times, particularly in warm dry weather.
gvmdaddy
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Post by gvmdaddy »

True, as you say Daewar, that it all very much depends on your route, uphill or downhill and head or tail winds etc.
Honestly though, when ive achieved around 80mpg on one run, ive never got less than 65mpg on the return along the same route, so the difference is not as great as you suggest.
Driving along at around 60mph is no great problem and neither is it dangerous as some people suggest. Its only jogging speed less than the law allows. I dont drive like this all the time, just when im not in a rush or payday feels too far away! Im much happier arriving at places 10 or 15 minutes later than if id been on the speed limit, knowing that im getting 20 to 30% better fuel economy.
Deleted User 3871

Post by Deleted User 3871 »

GVM,

I must admit, it must be my age, as im getting to enjoy driving slower and appreciating the benefits of fuel economy and catching a decent view, although my best is only 68mpg and i was driving like a nun.. I try to travel to work at 55mph on a 60 road and quite often im overtaken by other cars. Funny thing is though, a few miles down the road all the overtaking cars get stuck behind the same lorry, bus or tractor.

When towing a caravan on the motorway at 60mph is just not enjoyable. I've had lorries taking miles to get past me because they are 0.25 mph faster. They are supposedly professional drivers, then why are so many on the same part of the road as me driving like tits. I'm so glad i followed the instructions on installing a dash-cam, maybe we need a new area to show the footage!
gvmdaddy wrote: Sat Jun 17, 2017 6:37 pm True, as you say Daewar, that it all very much depends on your route, uphill or downhill and head or tail winds etc.
Honestly though, when ive achieved around 80mpg on one run, ive never got less than 65mpg on the return along the same route, so the difference is not as great as you suggest.
Driving along at around 60mph is no great problem and neither is it dangerous as some people suggest. Its only jogging speed less than the law allows. I dont drive like this all the time, just when im not in a rush or payday feels too far away! Im much happier arriving at places 10 or 15 minutes later than if id been on the speed limit, knowing that im getting 20 to 30% better fuel economy.
FLATT77611
Posts: 3
Joined: Thu Nov 03, 2022 10:09 pm
Qashqai Model: Mk.2 Qashqai Facelift - J11b (2017–2021)

Post by FLATT77611 »

On my 2020 Quasqai I have already covered over 50k miles mainly on longer journeys but the vehicle continually advises of oil changes after 9-10k so already now facing my 5th service. At £300-£400 per service I feel a bit ripped off. As far as I can see nothing in the manual advises of this, so my question to Nissan was have they miss sold me the vehicle, are the service periods set in the vehicle (or can the vehicle really”test” the oil, or are the service garage using an inferior oil? First response from Nissan was bland and avoided the question, no response as yet to my reply! Vehicle now going in for an ‘oil check’ this week could be an interesting visit!
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MikeGC
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Location: Stockport
Qashqai Model: Mk.3 Qashqai - J12 (2021+) New Model

Post by MikeGC »

Welcome to the forum Flatt7761
If I remember correctly the service interval is 18,000 miles or 12 months - which ever is first.
So with 50,000 miles you should have had at least two services (@ 18k minor & 36k major) and heading towards the third.
I don’t understand how or why your car could have flagged up that a service is required earlier than the set interval, unless there’s a way to alter the service interval warning in the car’s software.
The service staff have taken to heart "the customer is always right" and not asked why you are doing extra servicing
March '22 - J12 1.3DIG-T 160 CVT Tekna+ with all wheel drive - Pearl Black
July '19 - J11B 1.3DIG-T 160 DCT Tekna - Vivid Blue
March '17 - Qashqai J11A 1.5dci n-connecta - gunmetal
September '14 - Juke 1.5dci gunmetal ascenta premium (red accent packs)
FLATT77611
Posts: 3
Joined: Thu Nov 03, 2022 10:09 pm
Qashqai Model: Mk.2 Qashqai Facelift - J11b (2017–2021)

Post by FLATT77611 »

Hi MikeGC. My service book states 12,500 or 12 months. The service company refer to the DPF contaminating the oil, but my research indicates this only occurs if the engine (exhaust) does not reach a temper to burn off the residue, mainly short journeys! Most of my journeys are minimum 30 miles.
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