I use gear oil bottles and small bottles with the tip like the gear oil bottles have to put bar oil in my saws. It works pretty good and is better than carrying a big jug of oil around.
I use a small liquid tide laundry detergent bottle. Built in spout under the cap and it's bright orange and easy to keep track of.
20-24 oz pop bottles. about 2 fill ups a bottle (and the spouts are a good size for filling the saw) and on to the next and when working in the woods its a lot easier to have a bottle or 2 than having the gallon jug. I just fill a couple of bottles grab the fuel can, a couple chains and throw them in a work bag on the quad and leave the jug at the truck or in the shed.
If I am near the truck I work out of the gallon jugs I buy it in. Otherwise I usually fill up a pop bottle.
I use a gear oil bottle also but, I also found out that you can take the cap from the gear oil and put it right on a quart sized bottle of bar oil
I like the rectangle antifreeze jugs for in the woods gas and oil. They don't roll around in the skidder arch and won't roll down a hillside if your working on one. They fit nice in a milk crate which also keeps things neat in the back of the pickup. And they are free.