3 Causes Of Excessive Engine Oil Consumption

Before exploring the causes of excessive oil consumption, it is helpful to point out that all engines consume some oil through normal operation. Your engine oil forms a lubricating film between the moving metal parts of the engine. Some is consumed doing this, while some of the motor oil that is used near the combustion chambers is actually burned and becomes part of the vehicle's exhaust.

The definition of the term "excessive oil consumption" can vary, based on the vehicle specifications for its engine's expected normal oil consumption, usually found in the owner's manual. What one manufacturer defines as normal can be considered excessive by another carmaker. So the best place to start is your manual, which should spell out the normal oil consumption for your specific engine. This information is extremely useful for you to know, so that you can maintain the vehicle's proper oil level, while also keeping track of your consumption. For example, if a quart or more is consumed between oil changes, you will need to add oil to your engine to maintain its proper oil level. 

For example, General Motors states that oil consumption of one quart every 2,000 miles, for personal vehicles operated under normal conditions, is perfectly fine for its vehicles. Ford says one quart per 1,000 miles. BMW adds that "All engines normally consume a certain amount of engine oil." Volkswagen comments that "Oil consumption varies from engine to engine and may change significantly over the life of the engine." As the saying goes, your mileage may vary.

There can be a wide variety of mechanical issues that can lead to excessive oil consumption in your engine. Your engine oil's job is to circulate through your engine and lubricate the many moving parts that make it work. If a key mechanical part fails or wears out, oil consumption can increase to excessive levels. Some symptoms of excessive oil consumption caused by a mechanical issue can be blue smoke coming from your exhaust, substandard acceleration, and generally poor performance from your engine.

These mechanical issues can include a worn or damaged camshaft, connecting rod, or main bearings; worn crankshaft journals or main bearing seals; out-of-round cylinders; worn or broken piston rings or worn ring grooves; worn valve guides and/or valve stems; misaligned or bent connecting rods; a blocked air intake; clogged oil passages; worn timing chain or gears; a clogged PCV valve; a leaking turbocharger seal (if your engine has a turbo); and worn gaskets.

Since most of these mechanical issues are all happening deep inside your engine, it is highly likely that you will need to seek a mechanic's assistance to diagnose and repair the cause of your excessive oil consumption. Unless you have experience in tearing down and fixing engines, this is not a job for an amateur. 

The oil-related causes of excessive oil consumption include using the wrong oil, using dirty oil, and overfilling the oil beyond the maximum recommended level. Using the wrong type of oil for your engine is usually an issue related to the viscosity of the oil used. Viscosity is defined as the internal friction within the oil that resists its ability to flow. The lower the viscosity, the easier it flows at both low and high temperatures. 

Today's engines require lower viscosity oils to flow through their tighter passageways and to provide improved fuel economy. If the oil's viscosity is too low, excessive oil consumption or dilution of the oil by your fuel can result. If oil viscosity is too high, it can be consumed through evaporation when it stays on cylinder walls too long. 

Dirty oil usually results from not changing your oil at recommended intervals. You should never skip an oil change. Particles of dirt and other contaminants can build up in the oil, clogging the narrow lubrication passages and also increasing the wear on the many moving parts inside your engine. As these parts wear, your oil consumption will get even worse. Worst of all, dirty oil is consumed by your engine faster than clean oil. Overfilling your oil can be caused by not inserting the oil dipstick completely into your engine, giving a false reading. The excess oil can get splashed onto the cylinder walls and then burned in the combustion chambers, causing excessive oil consumption. 

Oil leaking from your engine is typically something that happens as your car gets older. As the mileage piles up, the gasket and sealing materials that are found between the metal parts of your engine can deteriorate and leak oil. The parts that once totally sealed the valve covers, the fuel and oil pumps, the oil pan, the camshaft bearings, and the timing cover can allow oil to leak out, as can parts like the oil lines and the oil drain plug.

Another issue to consider is the potential damage that can result from an oil leak, which can be either environmental in nature or can directly impact your car. Oil leaking from your vehicle is a hazardous material and can make its way into a storm drain, polluting the water supply. Oil is also a flammable material, and could potentially ignite and cause a fire under your car.

It can be difficult to calculate exactly how much oil is leaking. Once you detect an oil leak, you should check your oil level frequently to determine how much oil is being lost. Maintain an oil level that is above the minimum mark on the oil dipstick. If your oil level keeps dropping below the minimum mark with frequent checking, contact a mechanic right away and get the problem fixed ASAP.