Doctor Diesel

Particulately worried

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Dear Doctor, 

I recently had the good fortune to find a new shape 2010 BMW X3 2.0D for sale that only had 15,000 (verified) miles on the clock, and looked as good as the day it was driven out of the showroom. I just had to buy it! My previous vehicle was a Peugeot 3008 HDi 150 which had provided four years of excellent service. Anyway, driving the X3 is a complete joy, but Iím a little concerned about the diesel particulate filter (DPF) and regeneration. My understanding is that you need to be doing at least 2,000rpm in order for regeneration to work. At the motorway speed limit, my Peugeot would run at about 2,200rpm, but my X3 with its eight-speed automatic gearbox is still below the 2,000rpm mark. I am therefore concerned that, even if I do regular longer journeys, that regeneration might be a problem. One would hope that BMW has thought of this when selecting the gearing on their cars, but Iíd be grateful if you can put my mind at rest. Kind regards, 

James Tickle

Many thanks for your letter. I am very glad to hear that you have fallen in love with your X3, which I have always rated a fine car ñ the latter series, that is, as the previous one was about as close as BMW have ever come to producing a Lemon.

My own thoughts are to suggest that you manually drop the transmission into 5th or 6th gear (whichever comes closest to 2,500rpm) and cruise in that gear on the motorway for five to seven miles every few weeks, or maybe 400 to 500 miles. My concerns in your case, and I’m not setting out to worry you, relate to the car’s low mileage, that equates to just 3,000 odd miles a year. How those miles were covered we will never know, but it might be possible through a BMW garage to interrogate the ECU and find out if there are any historical problems with the engine. But thousands of BMW X3 owners are having no problems, and I hope my words of caution are not going to stress you. Some people drive so badly that they invite problems. Do keep an eye on the oil level, with the dipstick. A sure sign of DPF regeneration attempts that have not worked is a rising oil level, due to unburned fuel ending up in the sump. Check the oil level once a week and you will detect any early signs of such problems. But I am concerned enough to have asked BMW for an official line on this, a reply to which I will advise you of as soon as I have it! I will be in touch again as soon as I know more!

Doc D

P.S. The situation is, of course, partially a result of increasingly overpowered engines that very rarely have to work hard in normal, and legal, UK motoring conditions!

Hello again James,

I now have some words of wisdom from the BMW technical team, via the top man at the BMW media office. Pleasingly, it sounds a pretty encouraging response to me, and I don’t think that you should have much fear of any negative events. Should you experience any, it sounds to me that you are sensible enough not to just “hope the problems go away” as too many owners/drivers do, and get them sorted quickly, either by yourself, or with the help of your local BMW dealer.

BMW say:

“In this case the customer need not be unduly concerned. The engine speed is not so critical for BMW engines as the engine management system has the opportunity to regenerate the DPF through continuous higher speed driving, for example 70mph for a longer period. If the normal drive profile includes varied driving, there is no cause for concern. However, if the owner only does short journeys then a function exists in the car’s software to read the distance since last regeneration. Attention by a retailer will be able to advise if the regeneration can be completed through the normal driving profile. A lot of time and effort goes into the development of the engine management system on a BMW, so this and other operations should just go unnoticed by the customer.”

Best regards, and thanks for your letter James,

The Doc

One Response

  1. I have an elderly Toyota Estima diesel in Cyprus that is in pretty good shape at 18 years and 210,000km. Presently we are installing a Dry cell hydrogen generator that through hydrolysis, converts water to 2 parts H and 1of O. The gas is then fed directly to the air intake. This is well proven technology particularly in the USA so I am taking a punt as I am keen to reduce consumption, but more important to reduce particulates. Have you any experience of this modification?
    PS there is potential to improve consumption by 20% depending on the amount of H produced

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