If you have a rather old, diesel-engine vehicle, then you may understand that mechanical issues are to be expected from time to time, and you may have recently noticed a problem with your engine, as it seems to be down on power. You'd love to get to the bottom of this and provide your diesel service mechanic with more information, so they can get down to work and fix the issue without too much delay. Of course, it can be challenging for the average motorist to decipher any problems, but in this case, you may be able to get some clues from the colour of the exhaust smoke emanating from the back. What can this evidence tell you?

Black

While it is not always a clear-cut indicator of the problem source, the smoke can nevertheless be a good place for you to start. For example, if it seems to be predominantly black, then this indicates that you have an issue with the fuel-to-air ratio, and excess diesel is getting into the mixture. This could be due to a clogged air intake, which is preventing the proper amount of oxygen, or it could also indicate that you have issues with your fuel injectors. Sometimes, a faulty turbocharger can add to the melee and push some black smoke out of the exhaust.

White

In many cases, white smoke can be a good thing as it indicates that there are fewer impurities in the source of the conflagration, but in this case it's not necessarily so. In fact, white smoke can be particularly toxic, and you should avoid breathing it in if possible. In this case, the engine may be low on compression because the diesel fuel has been contaminated with water. The fault may lie in the pumping system, and while this is going on, you may feel as if the engine is very sluggish.

Blue

When the air is blue, it's time to worry. This is because your car is burning a lot more oil than it is supposed to, and in fact, it may be contaminating the fuel itself. In some cases, this may mean that the engine valve seals are faulty, or you may have a major problem with the cylinder head due to overheating.

What to Do Next

Some of these issues will require an urgent visit to your mechanic, but in every case, you need to take action if you are to avoid any deterioration. Remember that in an ideal world you should not see any smoke at all coming out of the exhaust, except perhaps at start-up.