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Change your oil

From OCAU Wiki

This is a basic guide to changing the oil in a four stroke piston engine as found in most cars. Thanks to Whitey Ford for his original guide posted in the forums.



Oil is used in engines to lubricate moving parts. It comes with a 'viscosity' rating. Viscosity can best be described as an oil's "thickness" and the rating has two numbers. Its cold viscosity and its warm viscosity. The first number is how thick the oil is when it is cold. The second number is how thick the oil is when it is operating at engine temperature. A rating of 20/50 means it is 20 when cold and 50 when warm.(edit)At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot. Most V8 and V6/i6 engines run 20/50. Most 4 cylinder cars run something around the 10/40 thickness, but consult your friendly spare parts dealer who will have a book that will show what thickness oil is recommended for your engine.(edit) Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if it is used.

Another important thing to consider is your oil filter. Some oil filters have 'anti-drainback' valves. From my knowledge, these include Ryco and Motorsport. This valve prevents the oil from draining back through the filter into your sump. If you buy a filter that doesn't have this, the oil must be pumped back through the filter at startup, which takes a few seconds longer, causing the top end of your engine to run unlubricated for the first few seconds longer than a filter with a "anti-drainback" feature.

Tools and parts

You will require the following:

  • Oil
  • Oil filter
  • Oil filter wrench
  • Funnel
  • Spanner (for sump plug, sizes vary)
  • Car ramps
  • Oil drain pan
  • Old shirt or rag


To change the oil in a car, first drive the car up on a set of ramps to raise the front of the vehicle. Engage the handbrake, put it in gear and chock the rear wheels. (edit)Covering the ground under the engine bay first with a cheap plastic dropsheet (available from painting stores or hardware stores for about $2) will help keep your work area clean and free from oil stains.

Place the oil drain pan under the sump plug. (edit)Remove excess dirt/oil/crud from around the sump plug with a clean rag, then remove the sump plug with the spanner to loosen and then remove by hand. As it loosens, oil will begin to flow from the hole into the drain pan. Make sure your car's engine is cool, otherwise the hot oil will burn your hand/face/body.

Allow oil to drain into pan. While oil is draining, remove your oil filter with your oil filter wrench. Most cars have the oil filter in difficult places and you will sometimes find that you can't reach it with the wrench. Automotive stores sell many different types of wrenches, select one that is appropriate for your engine bay. Failing that, try loosening it by hand (if you're strong and lucky) or if worse comes to worse, grab a cheap screwdriver and a hammer and puncture the oil filter with the screwdriver and loosen if from the engine by rotating the screwdriver. Use this as a last resort. Remove the filter completely and be careful not to tip it upside down, place it face down in your oil drain pan.

Now it's time to do something else while the oil drains from your sump, which should take up to two hours (depending on your sump capacity). It's usually a good oppotunity to check everything else in the engine bay (condition of belts and hoses) and top up anything like wiper bottle fluid etc.

Once oil has completely drained, refit the sump plug. Some people like to replace the sump plug washer as well, that's up to you, but they are cheap and really are a disposable item that are designed to be used once. Smear a small amount of oil around the rubber filter seal on your new oil filter and tighten it in place of the old one. Remove the oil filler cap (at the top of your engine) if you haven't already. Pour the required amount of oil into the hole, less 500ml. Allow it to settle in the sump and check your dipstick. Wipe the dipstick clean, and reinsert it into the engine, then recheck the level. Add remaining 500ml if neccessary. Check that the sump plug, filter and cap are tight and then lower the car. Start the car, make sure your oil pressure guage shows the correct pressure, or your oil pressure light goes out. Well done, you've just changed the oil in your car!


  • Never work under a jacked car.
  • Always make sure the engine is cold/cool.
  • Perform oil change on a flat, level surface.

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