Q. I wish to purchase a Mitsubishi Challenger (diesel only made) for my annual caravan trip. However the rest of the year ….

Q. I wish to purchase a Mitsubishi Challenger (diesel only made) for my annual caravan trip. However the rest of the year I use it only for the weekly shopping trip, and am concerned about the particulate filter blocking up. Your thoughts would be very much appreciated.

A.

As soot accumulates on the Particulate filter periodic cleaning is required to remove the deposits. The good thing about these filters is that they are self-cleaning. Self-cleaning occurs under certain operating conditions – the engine must be at operating temperature and the vehicle driven with moderate load at speeds greater than 40 km/h for approximately 20 minutes. If the vehicle is only driven for short distances, or if the vehicle speed is too low due to heavy traffic, the engine does not reach the required operating temperature. In these instances, the self-cleaning process may not have been able to complete. If the vehicle is driven for over 100km in these conditions, the vehicle will need to be taken to an authorised Mitsubishi Dealer as soon as possible. The vehicle can still be driven in this condition but it should be driven with low engine rpm, light loads and avoid high speed.

How much soot accumulates on the filter?

This depends on driving behaviour and driving conditions. If the vehicle is driven on short trips with light engine load, the self-cleaning process will occur more frequently. That is, more soot accumulates quicker.

Now, let’s re-consider your dilemma about purchasing a Mitsubishi Challenger. You mentioned that you will only take a single trip per year but the rest of the time it will be used for short weekly shopping trips. Assuming that you live in suburbia and not in the country where the closest supermarket is 20km away, the following can be summarised:

a) You driving the car on short trips means that soot will accumulate quicker in the filter, and

b) The probability of the self-cleaning process completing during your weekly short trips to the supermarket is unlikely.

My recommendation is that you steer away from any diesel car for the reasons stated above. Also, the single trip per year that you take that involves towing certainly does not justify buying a diesel car.