It's not all that uncommon to see a car spewing blue smoke everywhere, especially if it's an older vehicle. While this may seem harmless, it actually signifies a serious problem - your engine is burning oil when it shouldn't be.
The oil of a car is vital to it working, and it's frequently referred to as the lifeblood of a vehicle for good reason. Burning oil is not only bad because of the pollutants spewing out of the back of your exhaust pipe, but also because it means your car is in danger of burning up all of its oil. This can lead to a breakdown on the highway and cause further damage to your engine.
However, fixing the problem is easier said than done. For oil to get into the combustion engine and begin to burn, several things have to go wrong. For starters, there are likely worn-out or faulty valve seals and guides. This is what is supposed to prevent the oil from escaping, but if the oil is in the engine, then these aren't doing their job properly.
There are other possible causes for this issue as well, mainly related to the pressurization of the oil pan. If gas from another system is pushed into the area where the oil is, the oil can then get pushed out of its compartment and into the fuel delivery system. The car then thinks the oil is fuel and sends it to the engine. Not only does this result in burning, but it will decrease your performance and will likely damage the engine over time.
The two main reasons for this are blow-by from the piston rings and a clogged breather system. Like the oil valve seals, pistons are supposed to have their own rings that keep the system self contained. However, if these rings break or get worn down, combustion gases can escape into the oil system. Similarly, the breather system is responsible for allowing exhaust out of a vehicle. But over time carbon can clog the passageways and keep the exhaust gases in the system, which can then find their way to the oil and push it up into the fuel.
Regardless of the cause, burning oil is a major problem and one with no easy solution. Often, drivers do not catch the problem in time to prevent damage to their engine, which means that they may need a full rebuild or replacement - one of the more expensive repairs possible. Some drivers then reason that it's cheaper to just keep feeding their car more oil. However, this violates emissions standards and will not actually fix anything, just prolong the lifespan a bit. As drivers let the car burn more oil, they do more damage until the vehicle is essentially ruined. And if you ever forget to put oil in or underestimate how much you need, the entire engine will fail.
The blue smoke is a sign of this problem, but there are other things drivers should watch for as well. Oily spark plugs indicate that a seal is broken somewhere and oil is getting somewhere it's not supposed to be. In this case, it's just a matter of time before it begins burning off, so try to fix these leaks right away. This is also a problem that's easily spotted during an oil change, so be sure to perform those regularly in order to ensure that the oil in your car is not burning off.