Blue Smoke Emissions, Blue Exhaust Smoke

Blue smoke emissions or blue exhaust smoke are by-products of the engine oil burning in the combustion chamber. Usually this means engine oil is either escaping up past the piston rings due to wear in the cylinder walls or piston rings or leaking down from the valve stem seals. Occasionally it can be due to worn valve guides.

Providing nothing is broken (burnt valves, broken piston rings, worn-out catalytic converter) Ametech can help solve these problems with either one or a combination of products formulated to fill scratches in the cylinder walls and valve guides/stems or rejuvenate hardened valve stem oil seals.

When is it Blue Smoke?

So, you have a smoking engine. But is it blue smoke? What I mean is, how do you tell it's blue smoke, not white smoke or grey smoke? Sometimes it can be difficult to tell if it's blue. Blue smoke can be very pale, almost white, but it has a definite bluey tinge to it. It smells acrid - that's the burning oil; different to white smoke, which is water and coolant vapour and has a sickly sweet smell and different to a darker greyish smoke which is often due to over-fuelling and will smell like burning petrol or diesel fuel. Light grey smoke can also be caused by a dirty or torn air filter or maf (mass air flow) sensor and will usually be accompanied by a sluggish engine, maybe even an engine in limp mode. Thick grey smoke that doesn't go away is an indication of a serious problem, like a turbo failure, a turbo-charger eating its own oil supply or a stuck turbo. Any heavy and persistent smoke problem, whatever the colour the smoke, should not be ignored. Get your car to a mechanic as soon as possible!

The true test as to whether it's blue smoke is "Is the oil level going down on your dipstick?". Since blue smoke is a by-product of oil-burn, if your smoke is blue, your oil level will drop. Maybe only gradually, but it will drop.

When do you see the Blue Smoke?

Okay. So you've established that it is blue smoke? Now, when are you seeing the smoke? Is it there all the time? If it is, it's very likely that you've got a broken piston ring, or a burnt valve or valve seat, a holed piston or your cataytic converter is clogged or has failed.

Get your mechanic to carry out a dry/wet compression test, also called a 'leak-down test'. This will establish the extent to which air pumped into the cylinder when dry, with the valves closed, is able to leak out of the cylinder and will usually be able to pinpoint the point of escape. Air escaping past the piston rings into the crankcase would indicate worn rings/cylinder walls and shouldn't be a problem providing the percentage of leakage is low enough.

The test is repeated, but this time engine oil is squirted directly into the bore through the spark plug or injector hole. If the compression lifts, this is a good indication that there are no burnt valves, broken piston rings etc. and providing the leak down readings are not significantly high, Ametech products have a good chance of improving the compression and reducing the blue smoke emissions.

Blue smoke emissions on cold start is a familiar problem and occurs when the engine is first started after the vehicle has been left standing for some time. If you see this type of smoke first thing in the morning when you start your engine, it will often look a whitey blue colour and this is due to the condensation that has collected in the tail-pipe evaporating and mixing with the blue fumes from the oil-burn. This smoke usually clears within 10-15 minutes and you may not see it again till the next cold start. The most likely cause for this is shrunken and hardened valve stem seals. The valve stem seals should hold the oil back in the valve guides when the engine is off, but over time these rubber o-ring seals deteriorate, harden and shrink, allowing oil to drip into the combustion chamber overnight. When the engine is started, the oil which is now sitting on the piston head, gets caught in the combustion process, producing blue smoke, which will clear as soon as the oil has burnt off. Try a bottle of Oil Anti-leak to fatten up the valve stem seals.

Shrunken valve stem seals can also result in Blue Smoke whilst idling - most often seen at night caught in the headlights of the car behind while you are sitting at traffic lights. When you put your foot down to pull away from those lights you might see a puff of blue smoke emitted from your exhaust as you move off. What has happened here is that as you took your foot off the gas pedal approaching the traffic lights, vacuum has pulled oil through the shrunken valve stem seals into the combustion chamber. The oil has been fuming in the hot engine while it was idling and then ignites as you pull away, producing that cloud of blue smoke. Try a bottle of Oil Anti-leak to recondition the valve stem seals.

Blue Smoke on the overrun is again caused by vacuum sucking oil through the valve stem seals into the combustion chamber when you lift your foot off the accelerator coming downhill in 4th gear. You'll see that puff of smoke again when you put your foot back down on the gas.

The above problems, Blue Smoke on cold start, idling and on the overrun, can also be caused by wear in the cylinder walls, piston rings and valve guides and, more rarely, the valve seats. In this case, the blue smoke might be noticeable at other times too. Where shrunken valve stem seals have allowed oil to drip out from the valve guides, a depleted oil supply in the guides themselves can result in increased friction between the valve guides and stems, resulting in wear in the metal, particularly when starting the engine from cold. Use a can of Restore Engine Restorer in the correct dosage for your engine plus a bottle of Oil Anti-leak in the same engine oil to knock both problems on the head at the same time. Restore metal surfaces and rejuvenate oil seals to prevent leaks.

Dirty or clogged oil-ways in an engine can prevent the engine hydraulics from delivering sufficient lubrication to the cylinder/piston assembly during start-up, causing friction between poorly lubricated metal to cut wear into the cylinder walls and piston rings. Scratches in the cylinders walls allow oil to escape into the combustion chamber. The oil burns off as Blue Smoke. These are all possibilities that can't be ruled out. Clean the engine using a bottle of Motor Cleaner added to the old oil, fit a new filter to catch any muck released by the Motor Cleaner and then safely dispose of the dirty oil and used filters before refilling the engine with clean oil of the specification and grade recommended for your engine and fitting a permanent fresh oil filter. Most friction-induced wear (not worn valve seats though!) can be addressed with a can of Restorer Engine Restorer added into the fresh oil in the recommended dose.

If you're seeing Blue Smoke on hard acceleration- every time you put your foot down hard to accelerate or to get up a hill - you've got wear in the cylinders and piston-rings. You'll probably notice that the car is a bit sluggish too and you haven't got the torque in the higher gears to get you up hills. The engine will be more fuel thirsty too as it has to work harder to provide the power you're asking of it. These are all classic symptoms of cylinder wear and it's an ideal scenario for the application of a can of Restore Engine Restorer - filling scratches in the cylinder walls and piston rings to restore compression, reduce oil-burn, cure blue smoke emissions and restore fuel economy is what it does best.