Why Your Engine is Burning Oil

Telltale Signs Your Vehicle is Burning Oil

You are driving down the road and see bluish smoke in your mirrors. It’s coming from your vehicle’s exhaust. You want to ignore the smoke, but it’s getting darker. The bluish smoke coming your car’s exhaust is a sign that your car is burning oil. The thicker and darker the smoke, the more oil your engine is burning. This can be a real nightmare, especially in Arizona, because your car may need to pass an emissions test. If your car is burning oil, you can be certain your vehicle will fail emissions. There are four common reason’s why your car is burning oil. Some issues are easy fixes, others are not.

car exhaust spewing pollutionBurning Transmission Fluid

Burning transmission fluid is most common in vehicles manufactured in the 70’s, 80’s, and 90’s. This is because these older vehicles use rubber diaphragms to prevent the transmission fluid from leaking into the intake chamber. When the rubber diaphragms starts to fall apart from dry rot the transmission fluid leaks into the intake, and is burned in the combustion chamber. Locating the leaks can be difficult to spot, and can be dangerous the fluid is flammable. If you take your vehicle to an automotive shop they can use an exhaust analyzer to discover the type of leak and where it is located. This is a less common issue in newer vehicles as a new system is being using.

PCV Valve Defective

The PCV valve is the positive crankcase ventilation valve. The PCV valve removes blow by gases from the crankcase. When the valve does not work correctly the pressure from the gases builds up and can push out oil sealing gaskets. The blow by gas carries fuel that hasn’t been burned causing the engine oil to become diluted. The diluted oil is them burned during the combustion process. Some PCV systems may malfunction and oil will be sucked through the vacuum line. If you see fresh oil in the supply hose after removing the valve, it is likely the PCV valve is defective. Pressure techniques can be used to determine if this is the cause of the burnt oil. While it’s simple enough to hook a regulator to the PCV valve, it’s essential to have the proper amount of pressure. If too much pressure is used, it could result in damage that was not there before. When not enough pressure is used you won’t be able to locate the damage. Since this test is sensitive, you may want to have it completed at an auto shop.

valve cover gasketsWorn Valve Seal

If the blue smoke seems to clear a little while after starting your car cold, your car may be burning oil because of a worn valve seal. You will probably see a puff of blue smoke each time you start your car after it has sat a little while. Valve seals keeps oil from running down the valve stem and into the combustion chamber. As the seals wear out, small amount of oil begin to pass through them. If your vehicle is emitting the bluish smoke only when it’s started, and not while it’s running then it’s important to make checking the valve seals a priority. This is best completed when the engine is cold as the seals will be dry.

Worn Piston Rings

The final and most dreaded reason your car may be burning oil is due to worn piston rings. This is most common on high mileage vehicles. There are three rings in each piston. One ring controls the oil on the cylinder wall. The other two rings seal the combustion chamber. When the ring that controls the oil wears it leaves too much oil behind that is burned in the combustion chamber. A wet and dry compression test is used to determine the level of wear on the piston rings. The dry reading is taken first. A small amount if oil is then injected into the cylinder for the wet compression test. The result of the tests are them compared to the manufacturer’s specification. There are many reasons why the piston rings are wearing down, or sticking. A certified automotive shop is able to perform the tests and repair the piston rings without taking the engine apart if not necessary. It is always best to seek a second or third opinion before consenting to an engine replacement. For more information, please give us a call at (480) 641-8784 or just stop by our location. We look forward to hearing from you!