Even though the world is moving towards electric vehicles more and more, for the foreseeable future, most of us will be driving conventional cars, motorcycles, and trucks. Conventional vehicles like these produce emissions as a byproduct of the many complex processes taking place inside the engine, and assuming all of the vehicle’s parts are operating as intended, these emissions will find its way out of your car from the rear through the exhaust pipe.

With a healthy and well-functioning automobile, emissions are meant to be clear without any colour. However, there may come a time when you’ll notice coloured smoke exiting the vehicle, either from the back as intended or from the front where the engine is.

The first and most important thing to do is to remain calm. When in doubt, pull your vehicle over to the side of the road and park it somewhere safe. The colour of the smoke will give you an indication of what might be causing it, and where it might be originating from.

Let’s take a look at four common smoke colours and what they might indicate.

White Smoke

White smoke can mean two things, depending on the context. If you see white smoke come out of the vehicle’s exhaust when first starting a car, especially early in the morning when it's still cold outside, perhaps it's not smoke at all. What you’re seeing could actually be steam, caused by condensation taking place as the engine and the rest of the car warms up from the cold night before. As the engine warms up, the condensation should gradually reduce in just a few moments’ time.

However, if there is still thick white smoke coming out despite the car having warmed up, it could be the result of coolant leaking into the engine. This would be a very good time to get your vehicle to the mechanic as soon as possible so that they may look for the source of the leak and stop the issue from getting even worse.

Black Smoke

Black smoke on the other hand is slightly more common. Surely all of us driving down the highway have spotted other vehicles with thick black smoke coming out from the exhaust pipe, but what’s actually causing it? Well, black smoke is caused by the engine of your vehicle burning too much of its fuel, be it petrol or diesel. Again, the engine is a complex piece of machinery with many mechanisms working in tandem at any given time, and black smoke could be caused by one of these mechanisms not working properly.

Perhaps the issue is with the air filter, the various sensors, fuel injectors, or other parts that normally work in harmony to keep everything working without a problem.

While black smoke may not sound as serious of an issue as other colours of smoke, it could greatly affect your fuel economy if you do not resolve the issue quickly.

Blue Smoke

Blue smoke could be a bad sign, seeing as how it indicates the burning on engine oil. Not addressing this issue immediately could result in damage to your spark plugs, other than the damage that caused the leak in the first place, such as faulty seals and maybe even piston rings. Damage to these parts result in engine oil leaking from where it should be, that is lubricating the moving engine parts, into the actual chamber where fuel is burned.

Grey Smoke

Grey smoke is slightly more complicated to try and understand. The safest option, as usual, is to bring your car in to a workshop so a professional can perform the necessary diagnostic checks, but as a responsible car owner you’ll still want to understand the problem before you bring the car in.

Well, there are a few possibilities. Overall, grey smoke means that there is something leaking into the combustion chamber of the engine, something that shouldn’t be there. Leaks are typically caused by faulty gaskets or valves. As for the exact liquid leaking into the chamber causing the grey smoke emissions could be engine oil or even automatic transmission fluid (ATF).

As a final piece of advice: even though the best thing to do would be to bring your vehicle into the workshop to have it checked by professionals using the right diagnostics equipment, as a responsible vehicle owner, it’s always best to learn about the problem and its possible causes. This allows for you to learn more from your mechanic about such issues to prevent them in the future, and it also ensures that whatever mechanic you work with will remain honest, since they’re aware that you yourself know a thing or two about your vehicle.