For more complete information on taking care of your olympic bar, see our olympic bar maintenance article on Two Rep Cave, with links to the exact materials you should use for cleaning, how to disassemble and internally clean the bar, and more.
So you just got a new olympic bar and you want to keep it in good condition for years to come. It's a piece of cake if you know what to do.
First you may need to deal with any existing rust that is starting to form in spots.
If it's just a thin, smooth rust that doesn't wipe off on your hands, that's patina. Patina is an inactive rust that forms with very minimal exposure to moisture over time and will not get any worse. Some people even value it as a naturally formed coating that protects the steel.
For any other rust, you'll need to take some kind of brush to it.
For black oxide or bright/black zinc coatings, use a stiff nylon brush. Anything else will rub off the finish. And don't use a nylon brush with colored bristles. I tried that, and the red dye rubbed right off onto my bar. You want white or natural (yellow) colored bristles.
If the nylon brush isn't cleaning the knurling good enough, drip some 3-in-One oil (or mineral oil or gun oil) onto it to help mobilize the rust or gunk in the knurling.
For chrome or bare steel, a brass wire brush is safe. Brass is softer than steel and won't scratch it up. If that doesn't do the job, go with a stainless steel wire brush, which at least is softer than carbon steel. In either case, a drill mounted brush will be the easiest and most powerful.
First of all, if your bar came with a layer of dirty oil on it, wipe that crap off. That oil is put on at the end of the manufacturing process to protect the bar from corrosion while in storage and being shipped around the world. They seem to like to use a thicker brown oil for some reason. I'm no oil expert, so whatever. But wipe it off. You don't need that crap getting all over your hands, clothes, equipment and floor.
You can use a lot of different oils for lubricating and protecting the bar, including 3-in-One oil, mineral oil, gun oil, or any light machine oil (please don't use vegetable oil). WD-40 won't cut it. You need real oil.
Bare steel (aka : raw) bars need oil more than any other bars, given that there's nothing protecting it from moisture at all. Black oxide coated bars also need oil. The black oxide coating is designed to protect against rust only when it can interact with oil. I had a black oxide bar for a few years, but it was kept in the back room, not a garage, and usually with the back door closed, so the moisture exposure was limited to sweat. It did develop a patina pretty quickly where the black oxide had worn off in the center, but no rust. I rarely oiled it. If it were in the garage I wouldn't be so optimistic.
With other finishes, it's up to you. A stainless steel bar is protected against rust like nothing else, so unless it's actually stored outside then you don't need to worry about it. Chrome or zinc can use some oil.
But your bar doesn't have to feel oily or slippery. Here's what you do.
Wipe the oil all over the bar with a cloth, including the shaft and sleeves. Always use a lint-free cloth on your bar for cleaning or oiling, or the knurling will grab onto all the fibers it can and make a mess. Coat everything well. The oil protects the bar from being exposed to moisture. Leave the oil on overnight to give it time to fully penetrate into the surface. No need to leave it dripping, but make sure there's a thin layer over it.
In the morning, wipe the bar down good with a cloth to remove the excess oil. There will be a thin layer of oil left on the bar even after a good wiping down with a fresh cloth, and that will do the job without getting your hands oily when you use it.
Once you've done the above, you don't have to do much to keep your bar in great shape. Once a week or even once a month, brush the dead skin out of the knurling with a nylon brush, with the help of oil if necessary, and wipe it down with an oily cloth. I've heard of OCD people doing it every day. Once a week might be unnecessary. You might be able to go months. It depends on how much you sweat and how humid of an environment it's in. After several workouts you're probably going to rub off most of the oil from some parts of the shaft, or there will be enough salts from your hands that you want to get off.
If you use chalk, you'll need to clean the chalk out of the knurling with your brush EVERY DAY, and it's best to then wipe it down with oil. Chalk will attract moisture, which will cause rust in no time at all if you leave it there.
Storing a bar vertically can cause the oil inside the sleeves to gather at one end of each sleeve, so if you're going to do that, at least flip it over each time you put it back in (if you can keep track of the direction). A wall-mounted horizontal bar rack will avoid this issue.
For more complete information on taking care of your olympic bar, see our olympic bar maintenance article on Two Rep Cave, with links to the exact materials you should use for cleaning, how to disassemble and internally clean the bar, and more.