How much oil does it take? When do you add more? What happens if you over fill oil?
You add more when the level on the oil dipstick falls to–or below the “add” mark. At that point, add one quart.
The crankshaft of an engine, which is the main shaft that both drives the car, and that comes out of the front of the engine and has all the drive belts on it — the lowest spinning part. As it spins inside the engine, it whips the air inside the engine around. This whipped air is called windage.
If you overfill the engine with oil, the windage will start to whip the top surface of the oil, like waves on a body of water in the wind. If the oil level is close enough to the crankshaft, or the engine is spinning fast enough, the windage will tear drops of oil off the surface of the oil, and fling them around the inside of the engine. This can lead to a lot of oil on the cylinder walls, and therefore excessive oil consumption from the rings being unable to scrape away all that oil. Plus, this puts an oil mist in the air inside the engine. That oil mist will get sucked up by the Positive Crankcase Ventilation (PCV) system, leading to smokey exhaust, possible catalytic converter failure, and excessive oil consumption.
At this oil level the following can happen, but it is more likely with the oil level described.
It the oil level is high enough that the crankshaft actually is in the oil, the spinning of the crankshaft will directly splatter oil around inside the engine. This will froth the oil into foam, filling the airspace of the engine even more while it is running than it was at rest. This places a physical load on the crankshaft, possibly preventing the engine from idling, but certainly reducing mileage. The PCV system will probably start to pick up either liquid oil or oil foam. The PCV system has a vacuum hose and valve on one side of the engine, and an air supply on the other side, coming from the air filter. When the PCV system picks up liquid oil, the engine will receive a lot of oil, causing smoking and excessive oil consumption, but the passageway will be partially blocked as well. The exhaust gasses that get past the rings must go somewhere, and so air will go out of the crankcase air inlet. This air flow will take oil mist or liquid oil with it, and will put oil on the air filter, blocking the flow of combustion air a little (or a lot). Some of that oil will also be taken into the engine along with the combustion air, increasing the oil consumption of the engine, smoke in the exhaust, and possibly harming the catalytic converter.
Additionally, the seals at the ends of the crankshaft where it comes out of the front and rear of the engine are designed to control oil that is splattered onto the crankshaft, not the kinds of gushing oil described here, and they are not designed to work where there is pressure inside the crankcase, such as will happen if the PCV inlets and outlets get clogged with oil. Both the high volume of oil in the region of the crankshaft seals, and the possily elevated pressure can caus the seals to either be damaged, or possibluy only to allow exessive oil to escape. If the car has a manual transmission, that can put oil on the clutch necessitating replacing it. At the front of the engine, oil escaping can lubricate the timing belt if there is one, causing it to slip, and that causing the valve timing to be wrong, and that causing the valves and pistons to come into destructive contact.
Additionally, the drive belts (whether V belts or a serpentine belt) to slip, impairing battery charging, cooling (if the water pump slows down) and difficult steering (if the power steering pump slow down too much).
Now, it is true that some oil runs into the crankshaft and gets splattered around during hard acceleration or braking with a front-to-rear mounted engine, or hard cornering with a transverse mounted engine, so splattering oil around through direct contact with the spinning crankshaft is not automatically the death knell of engines, or our normal driving would cause all these things I have described. But it is a question of the amount. Some oil splattering around is normal under that kind of driving. But you cannot spend your whole trip speeding up, and you can;t spend your whole trip slowing down. You don't drive hard cornering all the time either. By the way, racing engines either do not carry the oil at the bottom of the engine, or they have additional sheet metal put into the oil pan to control the sloshing oil. Some race cars **** any oil that falls to the bottom of the engine out right away, and store it in a tank that is not part of the engine. This is called a dry-sump oil system.
But, since we don't drive in a way that sloshes the oil around all the time, but spend a good part of the trip driving at a steady speed in a relatively straight line, that amount of sloshing is not excessive enough to cause significant problems.
This was a fun question to ponder — thanks!
Jun 26, 2010 |
2000 Kia Sephia