Q&A for How to Add Oil to a Hydraulic Jack

Hydraulic oil is often mineral oil based, so it typically contains hydrocarbons. Hydrocarbons can be very dangerous if they enter the lungs, e.g. if someone swallows some of the fluid and accidentally inhales some of it. Always keep hydraulic oil away from children.

If you don’t have access to hydraulic jack oil, you can use machine oil or 10/20W lightweight motor oil in a pinch. Automatic transmission fluid will also work if you don’t have any other options. However, it’s not recommended that you use substances that aren’t designed for use in a hydraulic jack, since using the wrong kind of oil can damage the seals in your jack.

Hydraulic oil is a type of hydraulic fluid, but not all hydraulic fluids are oils. Other types of hydraulic fluids include water, glycols, and sodium-potassium alloys. Hydraulic oil serves as both a lubricant and a power-transfer medium in hydraulic machinery.

You should be able to remove the release screw/bolt (the thing you tighten/loosen to raise/lower the jack) completely and fill it from there with hydraulic jack fluid. However, it will be difficult to know when it's full. Keep that port facing up to avoid leaks. Test the jack every 2 ozs to ensure smooth operation. Stop filling if it seems to slip or fails to hold up under weight (you may even need to drain some).

Try depressing or opening the relief valve and pumping the jack 10-15 strokes, then close the relief valve and check for proper operation. This procedure should rid the system of any air trapped in the cylinder. Repeat if necessary.

Hydraulic oil should be used if at all possible. The additives in it are different from automatic transmission fluid.

No. Brake systems are hydraulic, but the fluid is very different form standard hydraulic oil.

Use jack oil, which is available from any auto parts store. Follow the manufacturer's instructions, but typically, oil should be added with the jack totally retracted.

Yes, it can, but it's not ideal. Try ATF if you really don't want to use hydraulic oil.

Yes. Over time moisture can find its way into the system and compromise the compression characteristics of the oil, making it dangerous to use the jack.

Lowering it completely will remove the air. Adding the fluid it will push any remaining air out.

The most likely problem is seal failure, allowing the hydraulic fluid to leak past the piston. Typically, the jack will extend when unloaded, but it will not lift a load. If it does not extend when unloaded, look for a stuck relief valve or mechanical damage.

Compression piston, load piston, relief valve, release valve, seals and fluid. You'll also need a lever to provide mechanical advantage to drive the compression piston(s), and a reservoir to hold and supply the hydraulic fluid. A floor jack will add a lever system to reduce the jack vertical profile and increase the amount of lift, a frame to hold all the parts together, wheels to roll it around and a pad to distribute load and keep the jack from shifting. Bottle jacks usually have a screw-type adjuster at the end of the load piston to take up slack, as their travel is relatively low. Most floor jacks are essentially a bottle jack on its side with a frame and lever system.

Yes, but you also can use ATF, which is cheaper than hydraulic fluid.

Yes, but the two are different. Compressors need oil that does not thin out at high temperatures and is designed primarily for lubrication. Hydraulic oils need to have additives that keep the oil from swelling seals and which provide corrosion resistance. While brake fluid is totally wrong for a hydraulic system and is almost impossible to purge once added, compressor oil will work in a pinch. You should drain and refill with the correct oil, once you can get to an auto parts store.

Open the valve 1.5 turns counterclockwise, then pump it fast 15 times. Then remove fill plug slowly; if fluid barely runs out, it's full.

Look for a rubber plug on the side of the cylinder. Older ones do not have a rubber plug. Some of them have a steel fitting fill plug.

For a floor jack, yes you can. It will work, but it's not what's recommended. I wouldn't risk it with anything else.

The piston should be in the full down position when filling the jack with oil.

Yes. Any kind of oil is fine. You only really run into problems with other fluids

1) Look at the end of the handle that goes to the bolt. The "bar" going across it that fits into the bolt may have broken off. A heavy duty, flat head, screwdriver will do the trick as easily. 2) Spray a little WD-40 or penetrating oil along the outer edge of the "release bolt." Wait about 5 mins, then try to turn it with the handle or screwdriver. 3) The oil "well" may be dry, leaving nothing but air! Fill it with hydraulic jack fluid.

Completely drain the "oil well" of any existing oil (you may need to turn the jack on its side or upside-down to accomplish this). Leave it to drain for a full day. After properly disposing of the used oil, refill the "well" with new hydraulic fluid (don't use any that has been around for more then 3 years unsealed or otherwise unprotected, especially if you live in an area with more than 50% average daily humidity).

Most jacks have only a single bolt, which leads to the oil well, as well as controls whether the jack goes up or down. Simply turn it counterclockwise until it comes out completely. In some cases, there is a separate bolt or similar mechanism where hydraulic fluid may be added (or removed). Regardless, such is usually clearly indicated on the jack with an arrow and the word "oil", "fill" or something along those lines.

Number one consideration is weight capacity, with a safety factor. Second consideration is lifting height. Also thing about installing jackstands vs tire change, stability required and frequency of use.