Mazda BT-50 Engine Problems

I wouldn't bother contacting Mazda, the car is seven years old and there's no proof that anything was amiss with it from new.

It could be the diesel particulate filter alerting you that it's doing its thing. DPFs regularly go through a regeneration process, and most do it while you're driving along without any real impact on the performance of the car.

Mazda tell us they have come across cam belt failures on the BT-50, but that it wasn't what they would refer to as a common concern, and not one they consider to have an abnormal rate of failure. From that you could deduce that it's not an unusual failure, but the failure rate isn't sufficiently high to do anything about.

We haven't heard of belt failures like you report, but it would be good to hear from any of our readers who have suffered the problem. It sounds like a serious one.

There are a number of heavy trucks running dual-fuel systems with a blend of diesel and natural gas, on some the gas is compressed (CNG) and on others it's liquefied (LNG). There are also other heavy truck systems that use diesel and LPG. We have reported on all of them over the past couple of years. In the case of light commercial vehicles the systems employed use diesel and LPG, substituting LPG for diesel, and as you say it needs to be very carefully controlled. The more LPG you use the more power you will get, but if it's not well controlled you run the risk of damaging the engine and that's very costly.

As Mazda pointed out to you the fuel consumption figures they publish are the results of laboratory tests mandated by the government. Every carmaker has to do the test and publish the results on a sticker on the windscreen of the car. As such it shouldn't be taken as fact that you will get the same figures when you drive the car in real life. The figures are given as a guide and for you to use when comparing one vehicle with another. There are many things that affect fuel economy, so you need to check everything that might cause your consumption to be higher and make sure you are doing everything you can in your driving environment to minimize your fuel consumption. Having done all of that it does seem that your vehicle is using too much fuel, as you say. I would engage your dealer and ask that he set up a fuel consumption test that measures the actual amount of fuel you are using so that both you and the dealer are in agreement about the fuel being used. You will then have a common basis on which to discuss what action you and the dealer could take going forward.

Comparing the fuel consumption of one vehicle to another can be tricky, even though they might seem identical. It can come down to the driving style, the terrain covered, tyre pressures, roof racks and bullbars fitted, size of trailer/caravan being towed etc. What appears obvious is not always so.