I’ve heard that doing short trips where the engine doesn’t get properly warmed up is not great for a diesel engine with a particulate filter. Is this true? If we gave it a spin up the dual carriageway for 20 minutes every couple of weeks would that be enough to keep it running OK?

I’m liking the super low road tax bracket that the small diesels typically fall into, hence the question.

Modern diesel cars are better suited for long journeys.

Italian tune up is good, but it defies concept of economical driving by revving engine high into 4K for 30minutes.

Using CataClean with italian tune up, helps clean out your system.Good product but costs monies. There are other fuel additives such as Millers or Forte products.

I personally use fuel additive Millers, and CataClean for italian tune up.

Certainly a problem with Japanese cars. My Mazda 6 burns off the deposits every 200 odd miles and squirts extra fuel in if the engine isn’t up to temperature. This fuel seems to make its way into the oil sump! Not been a problem for me so far.
VAG engine cars don’t seem to be an issue but I moved away from them because I found them troublesome.
If you do mainly town driving, stick to petrol.

You need a bit longer than 20 minutes, usually.

I’ve got a 1.3Multijet Doblo.

After a year of short journeys (50-100 miles a day), with a regen on the motorway once or twice a week, it felt like a bag of nails.
One injector failed and I had to have the DPF cleaned.
Better after a couple of years of more suitable use and a couple of full services, but it’s never quite felt the same since.

Still a great engine, but town work ruins them.

Sounds like you want a petrol car. Dieselsdont suit everyone

Small petrols are pretty economical these days. Tax is a red herring – its such a small percent of total motoring cost!

Never had a problem with my i30, it’s used as a shopping trolley most of the time about 100 miles per week. However I couldn’t be sure that it has a dpf. There’s conflicting info on the internet, we even struggled to get wipers for it.

I have a 2L diesel with DPF and it used to give me some issues but after the second failed regen I started throwing in Shell Vpower diesel and its much better behaved. Tried various additives, did nothing. It does a 6 mile journey twice a day through varying traffic and handles it fine but often gets a decent run at the weekend so that probably helps.

You can get the dpf removed….

I’ve heard that doing short trips where the engine doesn’t get properly warmed up is not great for a diesel engine with a particulate filter. Is this true?

Yes. The DPF is your main problem but there are others – other bits of the engine can coke up. It’s also not good for petrol cars incidentally, but much less of an issue.

Italian tune up is good, but it defies concept of economical driving by revving engine high into 4K for 30minutes.

30 mins! That’s way too long, and 4k is too high!

My Mazda 6 burns off the deposits every 200 odd miles and squirts extra fuel in if the engine isn’t up to temperature.

They all do this when the DPF gets clogged. Normal driving heats it up enough to burn it off, they squirt the fuel in if the exhaust gas isn’t hot enough.

This fuel seems to make its way into the oil sump! Not been a problem for me so far.

That’s normal for diesels, and it’s designed in. I remember reading somewhere that oils were designed to still work at 50% dilution with diesel!

You can get the dpf removed….

Please don’t. I don’t want your smoke in my kids’ lungs ta.

Thanks for the replies. This would be a Mini Clubman using the PSA diesel engine (so older than Autumn 2010). It would probably do around 5 miles a day in term time, but holidays would see it being used on longer motorway journeys.

Maybe petrol is best then…

I remember reading somewhere that oils were designed to still work at 50% dilution with diesel!

Up until recently I formulated engine oil for a living and I can tell you that’s utter bullplop. They’re not designed with any fuel dilution in mind although they can cope with some and even then it will be vehicle dependent. Mineral diesel dilution isn’t so bad as the diesel will evaporate out of the oil during a longer journey when the engine gets hot but running engines for short journeys or stop start conditions using fuel with a high amount of biodiesel can give huge fuel dilution as the biodiesel has a higher boiling point than mineral diesel and tends to stay in the sump instead of evaporating away.

Mineral diesel dilution isn’t so bad as the diesel will evaporate out of the oil during a longer journey when the engine gets hot

Ah yes.. maybe I’d misremembered, but I also remembe rreading that mineral diesel evaporates as you say. It was read in the context of why biodiesel can be bad for your engine.

Maybe petrol is best then…

I’m a diesel fan but even I’d say petrol is better for short trips. Petrol hybrid is better still of course 🙂

I think you’d be better off with petrol.

I had a Seat Leon with a DPF and for a few months it was only doing short trips. I thought no problem, can do longer runs to regen every so often. However when the car needs a regen doesn’t always fit nicely into your life and it was a pain driving extra miles to get the light out.

Please don’t. I don’t want your smoke in my kids’ lungs ta.

Umm, what do you think happens when the filter is clogged?
It dumps all that nice black soot out the back, usually in the countryside where you are doing a higher speed with more revs, as opposed to town driving.
That’s how they are designed to work. If they prevented all the bad stuff coming out, they’d be called a catalytic converter.

Whats your annual milege going to be?

5/day during term time it doesn’t sound like you’re gonna be doing anywhere near the 16-20k miles / year that *might* make a diesel more economical.

Filling the tank is the most tangible cost of motoring, but you must look at the entire costs. Purchase, Servicing, Fuel, Tax.

Diesels hit you hard on the first two, especially if the DPF / DMF / Turbo goes.

That’s how they are designed to work. If they prevented all the bad stuff coming out, they’d be called a catalytic converter.

DPFs are sort of semi-catalysts – when they are in regeneration there is a catalyst reaction and the ‘exhaust’ is not just what went in (soot), but it is oxidised and comes out as mainly CO2 – still not great, but better (for a given value of better…) than the black soot you would have got without a DPF

After a year of short journeys (50-100 miles a day)

Sorry… when did 100 miles a day become “short journeys”?

Umm, what do you think happens when the filter is clogged?

It heats it up and burns it into CO2. It does not dump it all out of the exhaust.

It wouldn’t be a filter if it let it all out would it?

If they prevented all the bad stuff coming out, they’d be called a catalytic converter.

Actually, there is a catalytic reaction involved in the regen cycle, IIRC. Your diesel also has a catalytic converter btw as well as a DPF.

The soot ends up in your kids lungs?! Lol!

If they lie on the pavement with their mouths a few inches away from the road maybe but otherwise not.

I’m sorry, the DPFs are just a money-making scam.

If you’re worried about particulates, then you should worry about tyre debris too.

The soot ends up in your kids lungs?! Lol!

If they lie on the pavement with their mouths a few inches away from the road maybe but otherwise not.

Where’d you read that?

The soot doesn’t travel far at all unless in a wind.

I’ll probably ditch my DPF pretty soon although my driving style ‘suits’ it. If ‘they’ want us to take part in the scam ‘they’ can make them free!

It’s worryingly naïve to think that microscopic particles only stay close to the road surface of moving vehicles. The World Health Organisation actually finally got around to defining Diesel exhausts as definitely carcinogenic in 2012. Now, they are not perfect by any means but probably know more about it than your mate down the pub…

Rachel

As mentioned before, a dpf is not a problem if its not there. It can be prefessionally removed and this will not affect the MOT.

5 miles a day in term time

hang on, this is singletrack – for 5 miles a day wouldnt you be better off on a bike? Then no need to worry about engine performance.

Removing the DPF IS a problem – the particulates that the DPF is designed to trap will now be expelled into the environment.

Please don’t do this…

Rachel

Rachel,

<sigh>

I’m sure they’re nasty. But there are bigger things to fleece people over than diesel particulates that aren’t a big problem

And no, not from a ‘mate down the pub’!

I had this very conversation with the salesman when I bought my last car. His assessment was that for the miles I do (typically 6-7 mile trips, approx. 6000 miles a year) the petrol would be the better option. Basically I wouldn’t be doing the mileage (a) to justify the extra cost of the diesel engine and (b) to make sure that the DPF wouldn’t clog up.

Diesels in town are poop, get a Petrol.

DPF Regen, typically, take 20 mins with the car (already warm) running at approx. 2000rpm – this raises the exhaust temps enough for the sensor to tell the DPF to start a regen cycle.

After market additives are shiv, use them to prevent a problem but not cure – it doesn’t work. Use decent fuel with additives in, it’s a false economy using poor quality fuel.

Diesels are more expensive to run = bollix. They only become expensive when they are used as run arounds. A diesel that only covers 6K a year on a motorway will be cost benefical vs a petrol doing the same (with today’s technology), change that 6K to town and it’s a different matter.

YOU DO NOT USE MORE OIL in a diesel when on the motorway than a petrol does, in fact you shouldn’t be using any, if your are you have a leak. If anything oil level will INCREASE in the sump due to failed DPF regen cycles.

I am in the business.

edit to add

removing a DPF is one thing to do, but needs doing properly as the ECU will need a remap and the sensor adjusting as it will freqk the ECU out.

Removing the DPF IS illegal for road going vehicles. If someone says otherwise, then please ask them to confirm what planet they are on.

I’m sure they’re nasty. But there are bigger things to fleece people over than diesel particulates that aren’t a big problem

And no, not from a ‘mate down the pub’!

I dunno what you mean.

How do you know particulates aren’t a problem, when the WHO think they are?

I think for any motoring under 20k miles a year, if you’re buying new, a petrol is the way to go.

Otherwise a previous generation diesel, without DPF and preferably with chain cam makes sense for normal mileage.

For short journeys; petrol new or second hand.

Diesels hit you hard on the first two, especially if the DPF / DMF / Turbo goes.

just to put this point in perspective

DPFs are fine (see above)
DMF – a lot of people going auto, so this doesn’t exist
Turbo – most new small engine petrols now have turbo’s

They only become expensive when they are used as run arounds.

Yeah or when people aren’t aware of how to look after them. I’ve heard stories about people owning cars that take the additive, and not being told about the need to fill the additive when they buy the car…

DMF – a lot of people going auto, so this doesn’t exist

Interesting you say that – there’s been some theorising on forums that an auto protects by keeping engine speed and torque within its parameters. Isn’t your claim a bold one? I hope you’re right anyway 🙂

Also re turbos, I suspect many problems are caused by low oil levels.

Mole, your point about the “additive” is a cerium additive (metal) which is a “main dealer” or indy serviceable “part”. The problem with this is that when home mechanics come into play, it’s not realised.

Ref the auto claim – yes it’s bold. If you take a typical new “autobox” you are looking at 8+ gears. They act more like the old CVT transmissions. With manuals, you tend to find less problems with DMF’s now anyway as torque delivery is being controlled better, until people go and re-map their cars 🙄

Oh.. I thought some cars needed something like ad blue? I dunno about cerium (goes off to Google)

EDIT I’m back:

Because smaller engines run at lower temperatures, a fuel additive may be required to promote regeneration. This additive, Eolys, is currently used on Volvo’s 1.6 and some 2.0 diesel engines where a DPF is fitted. The additive is a cerium/iron based solution that is added to a special tank under the fuel tank, which holds approximately 1.8 litres. Additive consumption is low and the tank is topped up as part of the car’s regular service schedule.

The fuel additive, whilst promoting regeneration to burn off soot particles, leaves a small ash residue which cannot be burnt off. It is therefore necessary to replace DPFs requiring the fuel additive at the 75,000 mile service interval.

Where the additive is not required, there is no need to change the DPF for the lifetime of the car, provided that regeneration is carried out as required.

Blimey.. so not only do you need to know if you need Eolys or not, if you do you also need to replace the DPF. That sucks.. but surely that’s not the £750 part people are complaining about?

oh yeah, that to! Yes, however adblue (Urea at 30 ish % solution) is a down exhaust /after treatment, these don’t usually harm the systems if run dry, just kills the emissions.

Removing the DPF IS a problem – the particulates that the DPF is designed to trap will now be expelled into the environment.

Please don’t do this…

I suspect the insurance companies would take a dim view of this and treat it as a modification as well. On the basis they will take any chance they can for a few quid.

Diesels are more expensive to run = bollix. They only become expensive when they are used as run arounds. A diesel that only covers 6K a year on a motorway will be cost benefical vs a petrol doing the same (with today’s technology), change that 6K to town and it’s a different matter.

That’s interesting. I was looking at a diesel (more or less because for most MPVs there’s little choice) and was slightly worried that I was being fooled by the pump price. We live rurally, so pretty much every time we use the car it’s 7/8 miles min.

ummm could the DPF give you issues if you accidentally ran the car on Petrol for a 15 miles till it cut out? i seem to have a power/limp mode problem since the fuel drain and new fuel filter.
interwebby tells me all sort of (horror) stories, including massive soot issues out the engine clogging up most things cos of higher burn temps of petrol…

there is no higher burn temp in a petrol, it’s lower (diesel boiling range is 140c upto 370c, petrol is 30c upto about 210c) , and also less soot producing. The petrol may well have “flooded” the dpf, but in more likelihood it’s fubar’d the sensor hence the limp mode.

Eolys is used in the Peugeot/Citroen versions of the 1.6 as well in case anyone was interested. I have to admit I didn’t realise that it caused the ash problem – normal DPFs will all have some ash content in them from regen but it is pretty tiny and hence no problem, had no idea the Eolys caused it to be a lot higher.

AdBlue is used for the reduction of NOx – although a side effect is that you can run a LOT less EGR if you have an SCR (Selective Catalytic Reduction – using AdBlue) which brings your soot down and so much slower and lower volume DPF filling.

BN, all other comments aside, yes diesel is more expensive per litre, but current savings on petrol cost is offset by more mileage. in your case however, short trips in a diesel is anightmare unless you can get a good run. Too many failed regen cycles will fill the sump with diesel thinning out the oil. Just get a V8 🙂