High engine temperatures and burned exhaust gases that also slip past the pistons turn oil into a thick mixture called sludge, which is anything but an ideal lubricant.
The typical American car requires five quarts of engine oil. Although most car manufacturers say that the oil filter need only be changed at every other oil change, the filter holds up to a quart of oil. Replacing the filter at the same time as the oil gives the engine a completely fresh charge of oil and, because the filter also is clean, insures the job will last longer.
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The engine should be warm so the oil will be sufficiently thinned to drain completely. Jack up the car and install safety stands, or drive the car onto ramps. Slip underneath with the proper wrench for the drain plug and a household pan to catch the oil. Exert a counterclockwise pull to loosen the plug.
It is easy to confuse clockwise and counterclockwise directions when lying underneath the car, and you may actually tighten the plug instead of loosening it. If you are unsure, try this – thread a bolt into a nut and take it underneath with you. Hold the nut and bolt with the nut upward and turn the bolt to unthread it from the nut. The direction you turn the bolt is the same that you should turn the drain plug.
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As soon as the plug is loosened, complete the unthreading by hand, with the household pan underneath the drain. When you get to the last few threads, apply finger pressure to hold the plug in the hole as you unthread it. When the plug is completely loose, held in place only by your fingers, quickly pull it away. This will prevent splashing oil on your arm.
Allow several minutes for the oil to drain out completely. Thread the plug in by hand, then tighten moderately with the wrench. Do not force the plug with the wrench. If you have to use force, you are probably cross threading, and the threads on both the plug and the oil pan will be damaged. The plug will not tighten properly, and even if it feels tight, it probably will loosen and soon leak oil.
If you aren’t sure, take out the plug and look at the threads carefully. If they are not damaged, clean them off with a small brush, such as the type from an electric razor. If they are damaged, do not panic and do not try to reuse the plug. The problem is not uncommon and auto parts stores carry kits to solve this problem.
Now pour the fresh oil into the engine. You can open the can with a can opener and pour through a funnel, or you can obtain a puncturing spout, which does both jobs and makes it easier to pour oil in without spillage.
by Robert Couse-Baker via Flickr
Where to pour in the oil may not be at all obvious to you if you have never done it before or watched a mechanic. Do not pour the oil unless you are sure.
After you have added the oil, check the engine’s oil level. This is done by inspecting the dipstick. To take an accurate dipstick reading, the car must be on reasonably level ground. Grasp the handle and pull out the dipstick from the tube. Wipe the oil off the tip of the dipstick, then reinsert it all the way. You may have to twist slightly to get it all the way down, so the base of the handle seats against the tube. Pull it out once more and read the level. Add half a quart of oil at a time, checking the dipstick reading after each addition, until the dipstick reads full.
Put on the oil cap, start the engine and let it idle for several minutes. Check the filter and the oil drain plug immediately, to see if there are any leaks. The odds are there will be no leaks, but if you spot a drip, stop the engine and find out why. It may simply be some oil you spilled on the engine as your were adding it, or the plug or filter may be loose and require additional tightening.
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After five minutes of operation, stop the engine and allow two to three minutes for oil to drain into the oil pan. Take another dipstick reading and you will probably find you must add some more oil. The reason for this is that the oil filter holds up to a full quart. When it is filled by the engine’s lubrication system the level in the oil pan is reduced. Top up as required to bring the dipstick level to full, and the job is done.