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Good advice

by Jake Venter on 24/01/2011

Comments: 0

I’ve been looking at the website www.honestjohn.co.uk It gives car-related tips and advice and I found one particular article quite interesting, but would also like CAR's opinion on the advice given, especially on the part about revving the engine every now and again.

It will also help me in establishing how reputable the site is. Question: what's the best way to run-in a diesel engine? Answer: leave the factory fill in the sump for the first year or 15 000 km and drive as follows:

1. For the first 1 600 km do not exceed 3 000 r/min, but make sure you reach this speed regularly.
2. For the next 1 600 km do not exceed 3 500 r/min, but make sure you reach this speed regularly. 3. For the next 1 600 km do not exceed 4 000 r/min but make sure you reach this speed regularly.
4. Finally, for the next 1 600 km do not exceed 4 500 r/min but make sure you reach this speed at least a couple of times a week.

After that, no limit, but make sure you continue to hit 4 500 r/min through the gears several times a week. The benefit of this is that it helps to self-clean the injectors, blow any accumulated soot out of the exhaust system and helps to free-off the piston rings. This makes the engine more efficient and less likely to use engine oil.

The site also mentions that a diesel particulate filter (DPF) is the latest bane of a diesel driver's life. On a passive cycle the DPF will require the car to regularly be driven significant distances at 2 000 r/min plus for the DPF to get hot enough to regenerate and burn off the particulates in it.

DPFs also have an active cycle where additional fuel is injected into the combustion chambers to create a hotter-than-normal exhaust gas to burn-off particulates in the DPF. However, this does not always work and the extra fuel can instead find its way into the engine sump, contaminating the lube oil and sometimes leading to such a rise in sump oil level that the engine can start to run uncontrollably on its sump oil and will self-destruct.

Peugeot/Citroën/Ford diesel engines don't need to get quite as hot as diesels in other makes because they use an additive to help regenerate the DPF. This used to be added to a tank under the back seat, but is now contained in a bladder that needs to be replaced around every 160 000 km.


The aim of a running-in period is to expose the engine to a gradually-increasing load so that the microscopic surface peaks that result from the machining process can be smoothed-off piece-wise, without any danger of overheating.

Consequently, running-in at a low constant speed will only take the process up to a certain level, and running-in at a high constant speed may result in overheating. The ideal is thus to vary the speed during runningin, but spend less time at high engine speeds or loads in the early stages.

This means that the above running- in advice is not wrong, but perhaps too complicated. Also, very few diesels are able to rev much past 4 000 r/min, so we would suggest that you reduce every one of the above limits by 500 r/min, and that you don’t exceed 4 000 r/min for any length of time, even after running-in. We’ve not heard of any problems associated with the DPF system, which is discussed in this issue in the article about buying a turbodiesel (see page 88).