Maybe you’ve seen it: at a stoplight, you are accelerating away, and the car ahead is blowing a bunch of blue-colored smoke out of its tailpipe. It’s not dramatic, like a smoke bomb, but it is also not normal like everyone else’s exhaust smoke.
Or maybe you experience blue smoke coming from your engine bay every morning at startup, regardless of the weather.
What is causing the blue smoke coming out of your exhaust, and how much is it going to cost to fix?
What Does Blue Smoke Mean?
Blue smoke means oil has mixed in with your gas during the combustion cycle. Your oil is being burned and released out of the exhaust pipe with the partially burned fuel and hydrocarbons.
This means your car is being inefficient in its operation, and these causes should be diagnosed as soon as possible. In many cases, the oil is leaking out from a bad gasket, which is not sealing all the way; this gives you some time.
If the blue smoke is coming from oil mixing with your gas in the combustion chamber, the finding is more urgent.
Reasons Your Car is Blowing Blue Smoke
#1. Oil is Leaking onto the Headers.
As I pointed out before, oil can seep from the gasket between your block and the head and drip onto your hot exhaust components of your drive train. This will make blue smoke, and it will be quite smelly.
You will most likely see some blue smoke coming from the rear of your vehicle as you’re accelerating or if you’re idling.
I will never forget the time I was checking out a 2002 Mitsubishi Montero. The owner said that she replaced the head gasket, and after just a short test drive, you could smell the oil burning and leaking from that same gasket she said was “fixed.”
More often than not, if the head gasket is bad, the cylinder head needs replacing, and the only reason your head gasket needs replacing is because it got so hot that it warped, allowing oil to seep into those spaces.
#2. The Oil is Mixing With Fuel.
Now, back to blue smoke. The valve seals, piston ring, and PCV valves in your car won’t last forever. And, if you’re going 10,000 miles between oil changes, your oil will be less effective as a friction reducer in your motor.
Due to increased heat in the engine and temperature cycles that heat and cool the gaskets, they dried out and cracked.
With dry and cracked valve seals, they will not do their job at sealing fluids from mixing, thus you will find that oil is mixing with your fuel, and the oil by-product is getting burned in the combustion chamber.
This means you previously had gray smoke coming out of your tailpipe, just like a normal day, but now you will see some blue smoke out of the exhaust system. If your piston rings are worn out, then you will need to replace your engine.
If this blue smoke just started occurring after an oil change, you may have simply put too much oil in it. This will allow the oil to froth up and not perform efficiently in heat and lubrication. You simply need to drain some oil out and start over.
#3. Oil is Dripping Onto Hot Engine Parts.
Another scenario goes like this: your head gasket and/or valve cover gasket went bad, and now your engine is leaking a bit of oil, which will drip down onto the other hot engine block, like the head, and then evaporate into a blue smoke cloud.
It will come out under your hood while you’re idling and then out the back of your car as you drive. This is another reason you should always be able to smell your car.
If you smell burning oil, is it a new smell? Did someone leave a double cheeseburger in the glove compartment? Ask yourself questions like these.
#4. Bad Glow Plugs (Diesel Engines).
If you notice blue or black smoke exiting your diesel car or truck upon startup, your glow plugs are most likely bad. This means your car will not start normally, and you will experience a longer-than-normal cranking time.
If you want to test and verify that the issue stems from your glow plugs, you can connect a test light to your positive battery terminal. Then, connect each of the wires to each of your glow plugs to see if there is a reading.
The price of replacing these could run anywhere from $100-$500, depending on whether you do it yourself or a reputable shop does it for you, so you want to be sure they’re bad before you spend the money.
Is it Okay to drive with Blue Smoke Coming Out of Your Tailpipe?
You can drive your car with blue smoke coming from your tailpipe, but like all of our recommendations, you should have it diagnosed by a qualified mechanic as soon as possible.
Simply because it is not a good thing to see oil mixing with your fuel, as that is not the way in which your engine was designed to run.
If the piston rings are wearing out and the vehicle has high mileage on it, then the engine will need to be replaced, which could put a bill of anywhere between $2500-$7000 into your hands, and that is money you will not want to spend.
You do not want to replace the vehicle’s engine, so go and get that issue checked immediately when the first signs of blue smoke appear. You may just have worn piston rings replaced and carry on running the car for a couple more years.
What If There’s Blue Smoke at Startup, Then It Goes Away?
Some initial small amounts of blue smoke emitted from the exhaust pipe during a cold engine startup are quite common with older, high-mileage vehicles.
Excessive blue smoke emitted from the exhaust pipe during startup, which takes a significant amount of time to dissipate, on the other hand, likely means the vehicle has worn internal components.
Blue smoke only identifies that oil has gotten past aged cylinder pistons and rings and is making its way to the combustion chambers.
As in the case with cold temperatures, there are increased gaps between the pistons and chamber walls that allow more oil to leak past. The engine warms up, so the components thermally expand, until they get hot enough to tighten the gaps somewhat to the point that the blue smoke/oil consumption reduces.
The Cost To Fix Your Blue Smoke Problem
Basically, you’ll either be replacing a glow plug, head gasket, valve seals, piston rings, oil separator, or PCV valve, depending on what caused the problem.
If you are handy and able to set aside some time (or scrape up a spare car), a valve seal is only $40…so this could be a cheap fix if you can put in the time.
If you are not handy with a tool, the part will cost $80 from any shop, and labor will be $500 +/-, which is pretty steep, but WAY less than a totaled car or a new engine!
That’s where it gets tough. If you have bad rings, chances are you are replacing the engine in that situation, which is super expensive, and could cost $7000 or more.
If your car is fairly new, that can be covered under the powertrain warranty, so ask the dealership first. If it’s an old used car and the engine is worth it to replace, you probably just need to suck up the cost.
The two most common scenarios in car shops are repairing the car or replacing the engine. For most people and insurance, replacing the engine is a total car, and so that is how the story of the blue smoke may end.
Drifting With Your Friends:
If you miraculously realize that the blue smoke is NOT coming from your piston rings, or valve seals, or head gasket, or PCV valve.
Or your crappy glow plugs, and you’re drifting on a track and blue smoke is blowing from ahead and your eyes are burning, then there’s a chance that the person in front of you has fancy tires that create colored smoke when they burn up! How rad is that?