'A bit of a run' for my car question

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Due to personal circumstances, our diesel car which was previously used for long journeys now mainly does town runs. So every now and then I give it an hour run at a steady 40-60 on main roads, to give the battery a chance and burn off diesel particulates. Other than the downside of burning a bit more fuel, do you think there’s any advantage to keeping the revs up by 500rpm, by driving in 4th gear instead of 5th? I’m thinking that the higher revs may assist particle burn and better charge the battery.
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Profile picture for user Bob

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I may be wrong but I think it would be better to get the catalyst up to working temperature to help with any particulates? (assuming your car has one). It's the short journeys that do the damage to cats - they rot from the inside out if not run at the correct temp. At least that is what I was told. If you think of the number of diesel taxis in London, for example, that never get above 30 or 40 mph and they seem to go on for ever, so as long as you run it on a regular basis there should be no battery problem (think modern batteries last longer than the ones of old?)...
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Thanks Bob, I knew there was something else but couldn't remember what it was. On one occasion the car lost the ability to accelerate while in the fast lane (very inconvenient and a bit exciting), it turned out to be a stuck exhaust gas regulator. Apparently the AA get loads of calls now for breakdowns due to particulate build up. So perhaps the odd long run, say once a week, helps avoid this.

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How old is the car (if you don't mind me asking)? Modern (under fifteen years old) catalytic-converters reach operating temperature very fast in order to meet very tight emission regulations; normal driving for half a mile or less. Particulates are more of a problem for passing the MOT test; and there are (legal) ways of avoiding problems.

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they rot from the inside out if not run at the correct temp. At least that is what I was told.
yes because it does not get hot enough to give it time to get rid of the moisture formed by combustion.
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Creaking Door, the car is aproaching 12 years old. It used to have problems passing the MOT due to particulates, but this became less of an issue as the years passed, the opposite of what I expected. Deliberate thread creep: I've had the car since new, and despite some fairly hefty expenditure recently (mainly a second-hand engine fit), I still think it's been more economical to buy it outright and run it into the ground (approaching 200k on the clock) than go down the PCP/HP route, swopping/paying for a new car every few years. A mate of mine swears by driving a banger to use as a daily runabout (when it breaks, he bins it and buys another for £500). Mind you, he is good with his hands and does most of the servicing himself. I wonder if anyone here thinks that PCP or leasing is cost effective?

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We have two cars; a twelve-year-old one we own and a two-year-old we lease. I keep scrupulous records of every penny I spend on them; I'll be very interested to see how they compare (although they are not identical models).

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When they MOT a diesel they check the 'particulates' (smoke / soot) by sucking a sample of the exhaust through a meter while revving the engine from idle to about four-thousand RPM several times. (This is why they'll often ask when your cambelt was last changed!) If you don't use high(er) RPM in normal driving (and most modern cars drive well without higher RPM) soot builds-up in the exhaust system (not the catalytic-converter usually) and this soot is blown into the 'smoke meter' during the MOT test; I think your car has to pass MOT soot limits three (or four) times out of five consecutive rev-ups! Immediately before your MOT go for a decent drive to warm your engine up (do NOT leave it idling as some MOT stations do!), use lots of revs, and just before you get to the MOT test-station, while coasting along, rev the engine to near the red-line a good five or six times (but don't over-rev it obviously). That will clear-out much of the accumulated soot and give your car much more chance of passing the MOT limits.

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...the car is aproaching 12 years old. It used to have problems passing the MOT due to particulates, but this became less of an issue as the years passed, the opposite of what I expected.
What did you have to do when it failed the MOT?
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Hi Rich Does it have a DPF or similar ? (diesel particulate filter) sometimes called FAP. It is the DPF which sorts out particulates - and they do have to get hot to work properly,it is why some modern diesels are completely unsuitable for short journeys (DPF does not get hot enough to operate). If it does not have a dpf then a good blast every now and again (as you are doing) should keep all ok,if it does have a DPF then a slightly faster motorway trip might be beneficial ! On the way to an MOT - I keep my cars in 4th to get the revs up and warm up quicker (country roads)
What did you have to do when it failed the MOT?
My 1997 pug 306 Turbo diesel just had a 'bit of a run' up to scotland and back over chrimble,but I MOT'd her just before the trip - the only failure was emissions and no advisories - a bottle of Forte cleaner in the tank apparently sorted the problem :D rgds baz

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On my old Citroen C15, I had to rev it now and again to clear out the soot. Best done when someone wouldn't get off my rear bumper :) The Berlingo turbo doesnt have the same problem.
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I run two classic sports cars a 1992 JDM 2.2 Honda Prelude vtec and a 1991 4.0ltr Lexus Soarer they are both exempt from emission tests. Both BTW would pass the tests. My Money goes into keeping them in pristine condition though. Still it is my hobby,I hate driving modern boxes with a short shelf(or shell) life.

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I wonder if anyone here thinks that PCP or leasing is cost effective?
If you prefer to keep your car up to date and avoid maintenance costs, then PCP or lease is the answer. However like yourself I prefer to own the car and change if and when I wish to do so. Had many years in the motor trade and never understood those who changed their car merely to drive a car with the latest plate, even though those customers were good for trade and me, personally my thinking was more on the lines that I have never yet managed to drive a number plate, was always more interested in the car attached to the plate.

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It is the DPF which sorts out particulates - and they do have to get hot to work properly,it is why some modern diesels are completely unsuitable for short journeys (DPF does not get hot enough to operate).
The trend with catalytic-converters has been to move them progressively nearer to (or into) the exhaust manifold so they get hot as quickly as possible; not sure what the current regulations are but the 'light-off' times are measured in seconds rather than minutes. Not so sure about DPF technology but I guess the same applies. I knew somebody who had a Ford Focus and that was fitted with a special fluid reservoir to clean the DPF. There must have been some fault with the vehicle (it was awful to drive!) because the fluid ran out (and it was supposed to last the 'life' of the vehicle I think?) and had to be topped-up; I think one litre of the special fluid cost £300!
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Yeah Peugeot/5hitroen use Eloys fluid in their DPF's,the 5hitroens have basically a plastic bag under the car which eventually deteriorates - result a red leak and expensive to sort and reset. My 1997 Pug 306 has three fifths of five eighths of of any complications and can lay a smoke screen that would please a ww2 destroyer skipper - although I no longer do that in deference to her age ; ) My much younger 5hitroen 1.6 Hdi is slightly too old to have a DPF (Gutted LOL :D) and after being remapped is quite a nice car to drive and benefits from cruise control etc...I took the old smoker to scotland for chrimble because of the expected weather - the 306 is lovely to drive and has just passed the 60,000 mile mark on the odometer... she is an absolute doddle for regular servicing items ! rgds baz
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Town driving and the DPF simply don't mix. If you really must drive a modern diesel on short town runs then one of the companies offering DPF removal should be your first port of call. EGRs are almost as bad and benefit from a regular clean out (A really nasty job I'm told by the guy who cleans mine) Moggy

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Town driving and the DPF simply don't mix.
Nah! You're just not using enough first and second gear! Can you get through an MOT with your DPF removed?
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Can you get through an MOT with your DPF removed?
Yes but it needs to appear to be still fitted ; ) One has to remove the internals through a hole in the casing and then weld it up again,the management light can then be massaged away electronically ! My 306 egr solenoid has been unplugged as well which means it is permanently closed off,because it is so old this does not put the management light on - on more modern cars the egr can be blanked and the management light massaged away electronically !
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And it's best if the engine is remapped at the same time to make it more efficient in the new set up. The guys who are good at this will do it all for you in half a day for not a lot of money and you end up with a much better car. I haven't had the DPF done, the S does mostly longer, faster trips. But I noted when we remapped Mrs Moggy's Megane that there were a lot of taxis / minicabs represented on the image wall at the remappers, there was even one in at the same time having its DPF bypassed. http://i4.photobucket.com/albums/y103/moggycattermole/P1030289-001_zps5bccd1c6.jpg Moggy
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Bit late popping back on here due to being on nights, but thanks for all your replies. Creaking Door, the car never failed the MOT, I think the guy just revved it to death until it passed, telling me it was very close. I like the idea of giving tail-gaters a 'surprise' and the MOT revving at the garage explains my alarm watching it being done - I thought they were trying to blow up the engine. Hi Baz, I don't know if my 03 Zaffy has a DPF or not, as usual I've been told different things by different garages. I know it's a different component, but After one garage told me the EGR needed cleaning out, another told me the other garage had identified the wrong component...talk about at the mercy of... One thing I am surprised about is the exhaust which I've never had to have any work done on other than remove the rusty outer bit around the big bit at the back. Silver Fox, I chuckled about your comment on driving the number plate. I saw this tv programme with a driver who changed her car every two years for the latest model. I looked at the PCP payments for doing so and you seem to pay massively for the privilege. I had virtually nothing go wrong (other than trivia) on my Zaffy for the first 100,000 miles or so, it was driven hard with 20,000 miles a year for the first five years. It cost £13500 new and even with £££ spent on another engine and lots of other stuff I still think over the 12 years it works out favourably. I might see if I can dig out the stats, kept all receipts etc. The only way I might consider a PCP is getting a car which doesn't depreciate much, like an Audi, but that's a bit of a pipe dream. I can't see myself ever being able to part with £25k+ unless I run into serious money. Baz, I wish I had your knowledge, you must have saved a fortune on garage bills but when I open up a bonnet I have to leave it to those who know what they're doing!

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Mines now a 14 year old Audi TT with 95k on the clock, it just passed its MOT again on the 27th of December, I get it serviced still by Audi as their fixed cost services are just as cheap as elsewhere, any problems found I buy genuine Audi bits but get them fitted by my local garage at a fraction of the labour cost... It has a full Audi service history so have kept it up since I got it, might sound daft at that age, but at least I know it's been done right with the genuine parts... The only bits it owes me since I bought it is two shocks, a boot, anti roll bar and a couple of drop links. The anti roll bar I fitted was a vr6 item as its a better and stronger item, and a straight fit.