Motor oil is supposed to course through your engine, providing a protective layer between the metal parts. As the parts move, the fluid provides lubrication. Without it, the parts inside the assembly would grind against one another, create friction, and eventually destroy each other. Motor oil prevents this from happening, and thus helps you avoid a costly repair bill.
In many cases, especially with vehicles that have high mileage, the engine begins to use oil at a faster rate than normal. Assuming you're checking the fluid level on a regular basis, you'll notice it drops quickly. We'll explain the reasons this happens below. None of the following will be pleasant news since it usually means expensive repairs are necessary.
Severely Worn Or Failing Valve Guides
During operation, the intake valves open to allow fuel into the engine's cylinders. The valves are connected to valve guides. Over time, the guides wear down, which impairs the valves' ability to seat properly. This allows oil to run down the guides into the cylinders.
Worn Piston Rings
Each cylinder contains a piston that moves up and down during the combustion cycle. The top of each piston has three rings. The top two rings regulate compression while the third ring controls the access of oil. If any of these rings wear down, fluid will be allowed to seep into the cylinders.
Is There An Oil Leak?
Another possible reason your car's oil level may be low is due to leaks. This is obviously unrelated to oil consumption, but is still worth mentioning since leaks can starve your engine of fluid. They can develop in several places, such as the valve cover gasket, oil pan gasket, and the front and rear crankshaft seals. They usually occur when heat causes the gaskets and seals to harden. They become less elastic.
In most cases, it happens so gradually (over several years) that the leaks go undetected. The leaks continue to grow larger until the driver notices his oil level plummeting. Fixing oil leaks may be a relatively simple job, or require lifting the engine from the vehicle.
Side Effects Of Worn Valve Guides And Piston Rings
So, what happens in your engine when the valve guides and piston rings wear down? In both cases, the assembly will experience a loss of compression. You may notice hesitation or sluggishness whenever you accelerate or place the engine under load. The severity of the hesitation is based on the compression deficit. The bigger the loss, the more sluggish the assembly.
Another problem is that the oil that gains access to the combustion chambers is burned alongside air and fuel. This causes excess deposits to form on the spark plugs. If the problem persists, the plugs will eventually become fouled.
Fouled spark plugs will cause your engine to misfire. This, in turn, creates a higher volume of emissions, which will escape through the exhaust valve. Not only will your car be likely to fail an emissions test, but the higher volume of hydrocarbons will cause your catalytic converter to work harder. It will eventually become plugged, and overheat.
Addressing The Problem
Of course, the most effective way to eliminate excess oil consumption is to fix the underlying problem. If the valve guides or piston rings are worn, have them replaced. Unfortunately, as implied earlier, both jobs are expensive, and particularly so given that the problem usually affects high-mileage vehicles. For this reason, a lot of people attempt to reduce the level of fluid consumption in their engines by taking other approaches.
There are additives that can help slow the rate at which your engine burns oil, but realize such fluids are a temporary fix. You can also use an oil with a higher viscosity. The higher the number, the thicker the fluid, and the slower the rate of consumption. Again, it's a short-term solution.
If you notice your car is using excess oil, pay close attention to the fluid level. Check it often, and replenish it when needed. Otherwise, you may find yourself stranded with an overheating engine.
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